Update vuln analysis GHAW to use on.push hook

This hook is needed for proper operation of the
`Vulnerability / CodeQL` job so that it can compare
before/after changes against the base branch.

I'm opting to skip limiting the pull_request hook
events to just the base branch, instead adding a
commented directive to imply that I explicitly
made that decision.

refs atc0005/todo#56

.github/workflows/project-analysis.yml

@@ -8,11 +8,17 @@
 name: Project Analysis
 
 on:
+  push:
+    branches: [master]
+
   pull_request:
     # `synchronized` seems to equate to pushing new commits to a linked branch
     # (whether force-pushed or not)
     types: [opened, synchronize]
 
+    # The branches below must be a subset of the branches above
+    # branches: [master]
+
 jobs:
   lint:
     name: Lint