Add Editorconfig,PHPStan and PHPCS to control code style

This PR adds an .editorconfig file which helps with a consistent code style and phpcs for checking the php codesytle before commiting files.

To use the editorconfig with PHPStorm install the Editorconfig plugin. For the use of phpcs and its precommit hook use composer install to install phpcs and the precommit hook. For phpcs functions in PHPStorm please follow https://www.jetbrains.com/help/phpstorm/using-php-code-sniffer.html#enabling-tool-inspection .