ci: add top level workflow permission to commitlint (#2449)

## Description
https://github.com/defenseunicorns/zarf/security/code-scanning/179

- [x] Test, docs, adr added or updated as needed
- [x] [Contributor Guide
Steps](https://github.com/defenseunicorns/zarf/blob/main/.github/CONTRIBUTING.md#developer-workflow)
followed

.github/workflows/commitlint.yml

@@ -5,6 +5,9 @@ on:
     branches: [main]
     types: [opened, edited, synchronize]
 
+permissions:
+  contents: read
+
 jobs:
   title_check:
     runs-on: ubuntu-latest