docs: added comment to GitHub actions yaml (#20)

Author: peter0083

.github/workflows/continuous-integration.yml

@@ -1,14 +1,21 @@
+# Github Actions workflow syntax documentation:
+# https://docs.github.com/en/actions/learn-github-actions/workflow-syntax-for-github-actions
+#
+# Useful Github Actions Triggers reference:
+# https://help.github.com/en/actions/automating-your-workflow-with-github-actions/creating-a-custom-action#triggers
+ 
+
 name: "Continuous Integration"
 
-on: [push, pull_request]
+on: [push, pull_request] # run unit tests on each commit so developers can notice errors as early as possible
 
 jobs:
   test:
     name: Unit tests 
     runs-on: ubuntu-latest
     timeout-minutes: 10
     strategy:
-      matrix:
+      matrix: # matrix testing strategy
         python-version: ['3.7', '3.8', '3.9', '3.10']
     steps:
     - name: Check out repository code