Add instructions to remove deleted JS / source map files in PR check

Author: henrymercer

.github/workflows/script/check-js.sh

@@ -14,8 +14,8 @@ npm run-script build
 # Check that repo is still clean
 if [ ! -z "$(git status --porcelain)" ]; then
     # If we get a fail here then the PR needs attention
-    >&2 echo "Failed: JavaScript files are not up to date. Run 'npm run-script build' to update"
+    >&2 echo "Failed: JavaScript files are not up to date. Run 'rm -rf lib && npm run-script build' to update"
     git status
     exit 1
 fi
-echo "Success: JavaScript files are up to date"
+echo "Success: JavaScript files are up to date"