fix: add explicit permissions to workflow

Add `permissions: contents: read` to module-checks-dev-requirements-change.yml
to restrict GITHUB_TOKEN scope following principle of least privilege.

Resolves CodeQL alerts #9 and #11 (actions/missing-workflow-permissions).

Author: weklund

.github/workflows/module-checks-dev-requirements-change.yml

@@ -15,6 +15,9 @@ on:
     paths:
       - "requirements-dev.txt"
 
+permissions:
+  contents: read
+
 jobs:
   get-modules:
     name: Get Modules