chore: add coverage directory to gitignore

Prevent coverage directory from being tracked when generated by external tools. Project coverage reports should go to tests/.phpunit/ as configured in phpunit.xml.

Author: wilcorrea

.gitignore

@@ -6,6 +6,7 @@
 .git/
 runtime/
 tests/.phpunit/
+coverage/
 vendor/
 .phpintel/
 .env