docs: add PHPStan detection logic to README

Signed-off-by: Maximilian Bösing <[email protected]>

Author: boesing

README.md

@@ -26,6 +26,7 @@ Currently, it identifies the following:
 - PHPUnit tests based on the presence of `phpunit.xml.dist` or `phpunit.xml` files.
 - phpcs checks based on the presence of `phpcs.xml.dist` or `phpcs.xml` files.
 - Psalm checks based on the presence of `psalm.xml.dist` or `psalm.xml` files.
+- PHPStan checks based on the presence of `phpstan.neon`, `phpstan.neon.dist` or `phpstan.dist.neon` files.
 - ComposerRequireChecker checks based on the presence of `composer-require-checker.json` file.
 - phpbench benchmarks based on the presence of a `phpbench.json`.
 - Infection mutation tests based on the presence of `infection.json` or `infection.json.dist`. In case that `roave/infection-static-analysis-plugin` is installed, this will be used instead.