Update usage example

Author: antonkomarev

README.md

@@ -50,6 +50,28 @@ php vendor/bin/php-db-migration-validator --rule=irreversible migrations/
 php vendor/bin/php-db-migration-validator --rule=irreversible app/migrations/ vendor/migrations/
 ```
 
+### Help
+
+```
+$ php vendor/bin/php-db-migration-validator help
+PHP DB Migration Validator
+--------------------------
+by Anton Komarev <[email protected]>
+
+Usage: php-db-migration-validator --rule=<rule> <path>
+
+  The following commands are available:
+
+    help  Shows this usage instructions.
+
+  Options:
+
+    --rules=<rule>   Validates the database migration(s) in the specified <path>.
+                     Exits with code 1 on validation errors, 2 on other errors and 0 on success.
+                     Available rules (at least one should be specified):
+                     - irreversible — ensure if migration file has `down` method and this method throws an Exception.
+```
+
 ## License
 
 - `PHP DB Migration Validator` package is open-sourced software licensed under the [MIT license](LICENSE) by [Anton Komarev].

bin/php-db-migration-validator

@@ -112,10 +112,10 @@ Usage: $binaryName --rule=<rule> \B<path>\C
 
   Options:
 
-    \Y--rules=<rule>\C   Validates the database migration(s) in the specified \G<path>\C are irreversible.
-                     The tool will try to check if migration file has `down` method and this method throws an Exception.
+    \Y--rules=<rule>\C   Validates the database migration(s) in the specified \G<path>\C.
                      Exits with code 1 on validation errors, 2 on other errors and 0 on success.
-                     \BAt least one rule should be specified.\C
+                     Available rules (\Bat least one should be specified\C):
+                     - \Yirreversible\C — ensure if migration file has `down` method and this method throws an Exception.
 
 EOF
         ,