Mention in README that the plugin is not thread-safe

Author: jozic

README.md

@@ -38,23 +38,25 @@ internal mojos:
 
 - **[pre-compile](http://scoverage.github.io/scoverage-maven-plugin/2.0.1/pre-compile-mojo.html)** and **[post-compile](http://scoverage.github.io/scoverage-maven-plugin/2.0.1/post-compile-mojo.html)** are internal goals, they configure Maven build in forked `scoverage` life cycle; don't use them.
 
-Maven generated plugin documentation:
+### Maven generated plugin documentation
 
 | Version       | Documentation                                                                                 |
 |---------------|-----------------------------------------------------------------------------------------------|
 | `2.0.1` | [Plugin Info](http://scoverage.github.io/scoverage-maven-plugin/2.0.1/plugin-info.html) |
 | `1.4.11`      | [Plugin Info](http://scoverage.github.io/scoverage-maven-plugin/1.4.11/plugin-info.html)      |
 
-##### Prerequisites / limitations
+### Prerequisites / limitations
 
-Plugin is compatible with two Maven Scala compiler plugins:
+- Plugin is compatible with two Maven Scala compiler plugins:
 
-- [SBT Compiler Maven Plugin](https://github.com/sbt-compiler-maven-plugin/sbt-compiler-maven-plugin/) - version **1.0.0-beta5** or later required,
+    - [Scala Maven Plugin](http://davidb.github.io/scala-maven-plugin/) - version **3.0.0** or later required, [addScalacArgs](http://davidb.github.io/scala-maven-plugin/compile-mojo.html#addScalacArgs) and [analysisCacheFile](http://davidb.github.io/scala-maven-plugin/compile-mojo.html#analysisCacheFile) configuration parameters cannot be set directly, use project properties 'addScalacArgs' and 'analysisCacheFile' instead.
+  
+    - [SBT Compiler Maven Plugin](https://github.com/sbt-compiler-maven-plugin/sbt-compiler-maven-plugin/) - version **1.0.0-beta5** or later required, works with scoverage-maven-plugin 1.4.11 or earlier
 
-- [Scala Maven Plugin](http://davidb.github.io/scala-maven-plugin/) - version **3.0.0** or later required, [addScalacArgs](http://davidb.github.io/scala-maven-plugin/compile-mojo.html#addScalacArgs) and [analysisCacheFile](http://davidb.github.io/scala-maven-plugin/compile-mojo.html#analysisCacheFile) configuration parameters cannot be set directly, use project properties 'addScalacArgs' and 'analysisCacheFile' instead.
+- Plugin is not thread-safe, so it should not be used in multi-threaded builds.
 
 
-##### Scoverage Maven plugin version
+### Scoverage Maven plugin version
 
 This can be set as project property.
 
@@ -67,7 +69,7 @@ This can be set as project property.
 ```
 
 
-##### Scala version configuration
+### Scala version configuration
 
 Plugin supports Scala 2.12.8+, 2.13.0+ and 3.2.0+ versions by automatically loading and configuring matching `scalac-scoverage-plugin` Scalac SCoverage Plugin artifact. For this to work Scala version has to be set. It can be done by defining `scalaVersion` plugin configuration parameter or `scala.version` project property. Without this setting, coverage will not be calculated. 
 
@@ -115,7 +117,7 @@ The first method is better because once the property is defined it's value can b
 
 For Scala 2.10 and 2.11 support please use Scoverage Maven plugin `1.4.11`.
 
-##### Scalac SCoverage plugin version configuration
+### Scalac SCoverage plugin version configuration
 
 Maven SCoverage plugin uses by default the latest version of the [scalac-scoverage-plugin](https://github.com/scoverage/scalac-scoverage-plugin) available on its release day.
 If newer, better version of [scalac-scoverage-plugin](https://github.com/scoverage/scalac-scoverage-plugin) is available, it can be used instead.
@@ -149,11 +151,11 @@ or
 </project>
 ```
 
-##### Integration tests coverage check and reports
+### Integration tests coverage check and reports
 
 `integration-check` and `integration-report` mojos are similar to `check` and `report` mojos, but they execute forked `scoverage` life cycle up to `verify` phase (integration tests are usually executed in `integration-test` phase).
 
-##### Aggregated reports for multi-module projects
+### Aggregated reports for multi-module projects
 
 There is no separate mojo for aggregated reports, there is `aggregate` parameter.
 To additionally generate aggregated SCoverage report for root module, when generating regular reports,
@@ -261,7 +263,7 @@ or in `reporting/plugins` section when adding report to Maven generated site
 </project>
 ```
 
-##### Adding SCoverage report to site
+### Adding SCoverage report to site
 
 Add plugin to reporting section of your project and configure it to generate one of reporting mojos.
 By default Maven executes all plugin's reporting mojos, but SCoverage plugin has three such mojos
@@ -299,7 +301,7 @@ Which reporting mojo should be selected:
 | [integration-report](http://scoverage.github.io/scoverage-maven-plugin/2.0.1/integration-report-mojo.html) | When using integration tests                                                                                                                                                                                                                            |
 | [report-only](http://scoverage.github.io/scoverage-maven-plugin/2.0.1/report-only-mojo.html)               | When coverage data was already generated (usually by [check](http://scoverage.github.io/scoverage-maven-plugin/2.0.1/check-mojo.html) or [integration-check](http://scoverage.github.io/scoverage-maven-plugin/2.0.1/integration-check-mojo.html) mojo) |
 
-##### Customizing code instrumentation
+### Customizing code instrumentation
 
 If you want to customize plugin's configuration parameters used by compilation supporting part of the plugin, do it in 'plugins' or 'pluginManagement' section:
 ```xml
@@ -325,7 +327,7 @@ If you want to customize plugin's configuration parameters used by compilation s
 Read [SBT SCoverage Plugin documentation](https://github.com/scoverage/sbt-scoverage) for more information about [highlighting](https://github.com/scoverage/sbt-scoverage#highlighting) and [excludedPackages](https://github.com/scoverage/sbt-scoverage#exclude-classes-and-packages).
 
 
-##### Checking minimum test coverage level
+### Checking minimum test coverage level
 
 ```xml
 <project>
@@ -362,7 +364,7 @@ Run `mvn scoverage:check` to perform the check. See below if you want to use `mv
 Read [SBT SCoverage Plugin documentation](https://github.com/scoverage/sbt-scoverage#minimum-coverage) for more information. 
 
 
-##### Checking minimum test coverage level AND adding report to site
+### Checking minimum test coverage level AND adding report to site
 
 ```xml
 <project>
@@ -409,7 +411,7 @@ Read [SBT SCoverage Plugin documentation](https://github.com/scoverage/sbt-scove
 Run `mvn scoverage:check` to perform the check and `mvn scoverage:report` to generate the report.
 
 
-##### Checking minimum test coverage level automatically
+### Checking minimum test coverage level automatically
 
 If you want `mvn verify` and `mvn install` to check the coverage level, you have to change your POM
 so that SCoverage takes over running all the tests.