GH Actions: move docker build to seperate job

Author: equinox0815

.github/workflows/release.yml

@@ -23,6 +23,11 @@ jobs:
         extra_files: AUTHORS LICENSE LICENSE.zxcvbn README.md doc/man/whawty-auth.8
         md5sum: false
         sha256sum: true
+  docker:
+    name: Build and Publish Docker Image
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v3
     - uses: VaultVulp/gp-docker-action@1.6.0
       with:
         github-token: ${{ secrets.GITHUB_TOKEN }}