fix:[close #183] Restrict differ to dev branch only

Add branches definition to differ workflow

Change container ref to match branch name

.github/workflows/differ.yml

@@ -3,14 +3,15 @@ name: Differ
 on:
  workflow_run:
  workflows: [Vib Build]
+ branches: [dev]
  types:
  - completed
 
 jobs:
  differ:
  runs-on: ubuntu-latest
  container:
- image: ghcr.io/vanilla-os/desktop:main
+ image: ghcr.io/vanilla-os/desktop:${{ github.ref_name }}
  if: github.repository == 'vanilla-os/desktop-image'
 
  steps: