Instructs user to call cleanup() themselves

Author: kyle-n

docs/preact-testing-library/api.mdx

@@ -54,6 +54,7 @@ Unmounts the component from the container and destroys the container.
 
 > This is called automatically if your testing framework (such as mocha, Jest or
 > Jasmine) injects a global `afterEach()` function into the testing environment.
+> If not, you will need to call `cleanup()` after each test.
 
 If you'd like to disable this then set `process.env.PTL_SKIP_AUTO_CLEANUP` to
 true when running your tests.

docs/react-testing-library/api.mdx

@@ -291,6 +291,7 @@ Unmounts React trees that were mounted with [render](#render).
 
 > This is called automatically if your testing framework (such as mocha, Jest or
 > Jasmine) injects a global `afterEach()` function into the testing environment.
+> If not, you will need to call `cleanup()` after each test.
 
 For example, if you're using the [ava](https://github.com/avajs/ava) testing
 framework, then you would need to use the `test.afterEach` hook like so:

docs/svelte-testing-library/api.mdx

@@ -72,6 +72,7 @@ const {results} = render(YourComponent, {myProp: 'value'})
 
 > This is called automatically if your testing framework (such as mocha, Jest or
 > Jasmine) injects a global `afterEach()` function into the testing environment.
+> If not, you will need to call `cleanup()` after each test.
 
 Unmounts the component from the container and destroys the container.
 

docs/vue-testing-library/api.mdx

@@ -234,6 +234,7 @@ Unmounts Vue trees that were mounted with
 
 > This is called automatically if your testing framework (such as mocha, Jest or
 > Jasmine) injects a global `afterEach()` function into the testing environment.
+> If not, you will need to call `cleanup()` after each test.
 
 Failing to call `cleanup` when you've called `render` could result in a memory
 leak and tests which are not idempotent (which can lead to difficult to debug