Update release GitHub action to deploy to DockerHub

The release pipeline now should build and push the c2g image to DockerHub
when building a tag, tagging the image with the tag's version number
as well as with "latest".

.github/workflows/release_tag.yml

@@ -54,3 +54,21 @@ jobs:
           files: 'c2g*'
         env:
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN  }}
+
+      - name: Login to DockerHub
+        uses: docker/login-action@v1
+        with:
+          username: ${{ secrets.DOCKERHUB_USERNAME }}
+          password: ${{ secrets.DOCKERHUB_TOKEN }}
+
+      - name: Get tag
+        uses: olegtarasov/[email protected]
+        with:
+          tagRegex: "v(.*)"
+          tagRegexGroup: 1
+
+      - name: Docker build and push
+        uses: docker/build-push-action@v2
+        with:
+          push: true
+          tags: tomasfarias/c2g:${{ GIT_TAG_NAME }},tomasfarias/c2g:latest