Added documentation and pull_request

Author: ArminJo

.github/workflows/LibraryBuild.yml

@@ -1,9 +1,15 @@
+# LibraryBuild.yml
+# Github workflow script to test compile all examples of an Arduino library repository.
+#
+# Copyright (C) 2020  Armin Joachimsmeyer
+# https://github.com/ArminJo/Github-Actions
+#
 # Before being able to push to my .github\workflows directories,
 # I had to create a new personal token with workflow enabled at https://github.com/settings/tokens
 
 # This is the name of the workflow, visible on GitHub UI.
 name: LibraryBuild
-on: [push]
+on: [push, pull_request] # see: https://help.github.com/en/actions/reference/events-that-trigger-workflows#pull-request-event-pull_request
 
 jobs:
   build: