Add phpcs to github workflow (#66)

Author: janlam7

.github/workflows/main.yaml

@@ -33,3 +33,5 @@ jobs:
           run: composer install --no-progress --prefer-dist --optimize-autoloader
       -   name: phpunit
           run: php vendor/bin/phpunit
+      -   name: phpcs
+          run: php vendor/bin/phpcs

phpcs.xml.dist

@@ -1,5 +1,6 @@
 <?xml version="1.0"?>
 <ruleset name="Hostnet PHPCodeSniffer Standard">
   <rule ref="Hostnet"/>
-  <exclude-pattern>*.inc</exclude-pattern>
+  <!-- Copied from mediawiki-codesniffer -->
+  <exclude-pattern>src/Hostnet/Sniffs/Classes/MultipleEmptyLinesSniff.php</exclude-pattern>
 </ruleset>