Add header-checking function (#9880)

* Add basic header-checking function

* Add Slack notification logic

* Modify Netlify Functions setup

* Rework function logic

* Add missing dependencies

* Remove package-lock.json from Git

* Separate header checking function

* Isolate env check into a separate function

.gitignore

@@ -32,3 +32,8 @@ public/
 
 # User-specific editorconfig files
 .editorconfig
+
+# Netlify Functions build output
+package-lock.json
+functions/
+node_modules/