Chore: do not run husky hooks on backend-only changes (grafana#48439)

Author: zserge

.husky/pre-commit

@@ -1,4 +1,8 @@
 #!/bin/sh
+
+# Ignore husky hooks if no frontend code has been changed
+git diff --cached --name-only | grep -v --quiet "^pkg/" || exit 0
+
 . "$(dirname "$0")/_/husky.sh"
 
 yarn run precommit