Add check for forks when running PR workflows (#432)

Author: MattyTheHacker

.github/workflows/update-dev-container-image.yaml

@@ -12,6 +12,7 @@ jobs:
       packages: write
 
     if: ${{ ! startsWith(github.head_ref, 'dependabot/') }}
+    if: ${{ github.event.pull_request.head.repo.full_name == 'CSSUoB/TeX-Bot-Py-V2' }}
 
     steps:
     - uses: docker/setup-buildx-action@v3