gha: run codeQL on PRs, and add comment for cron

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

.github/workflows/codeql-analysis.yml

@@ -6,6 +6,15 @@ concurrency:
 
 on:
   schedule:
+    #        ┌───────────── minute (0 - 59)
+    #        │ ┌───────────── hour (0 - 23)
+    #        │ │ ┌───────────── day of the month (1 - 31)
+    #        │ │ │ ┌───────────── month (1 - 12)
+    #        │ │ │ │ ┌───────────── day of the week (0 - 6) (Sunday to Saturday)
+    #        │ │ │ │ │
+    #        │ │ │ │ │
+    #        │ │ │ │ │
+    #        * * * * *
     - cron: '0 12 * * 6'
   push:
     branches:
@@ -14,6 +23,10 @@ on:
     tags:
       - 'v*'
   pull_request:
+    # The branches below must be a subset of the branches above
+    branches:
+      - 'main'
+      - 'release/*'
 
 permissions:
   contents: read # to fetch code (actions/checkout)