ci: Tag docker image with tag name

See https://github.com/tus/tusd/issues/511

.github/workflows/main.yml

@@ -59,3 +59,18 @@ jobs:
       run: |
         docker build -t tusproject/tusd:$GITHUB_SHA .
         docker push tusproject/tusd:$GITHUB_SHA
+    - name: Tag docker image with release tag
+      if: startsWith(github.ref, 'refs/tags/')
+      run: |
+        # Extract tag name: https://stackoverflow.com/a/58178121
+        TAG_NAME="${GITHUB_REF#refs/*/}"
+        docker tag tusproject/tusd:$GITHUB_SHA tusproject/tusd:$TAG_NAME
+        docker push tusproject/tusd:$TAG_NAME
+        # Create latest tag if we have no pre-release
+        if [[ $TAG_NAME =~ ^v\d+\.\d+\.\d+$ ]];
+        then
+          docker tag tusproject/tusd:$GITHUB_SHA tusproject/tusd:latest
+          docker push tusproject/tusd:latest
+        fi
+      shell: bash
+