add links to the documentation to the github workflow files

.github/workflows/clean-up.yml

@@ -1,3 +1,6 @@
+# GitHub Action to remove old artifacts
+# Documentation: https://github.com/c-hive/gha-remove-artifacts
+
 name: clean-up
 
 on:

.github/workflows/main.yml

@@ -1,3 +1,6 @@
+# Automate, customize, and execute your software development workflows right in your repository with GitHub Actions.
+# Documentation: https://docs.github.com/en/actions
+
 name: build
 
 on: [push, pull_request]