CI: build and publish docker images

.github/workflows/linux.yml

@@ -31,6 +31,12 @@ jobs:
             target
           key: ${{ runner.os }}-cargo-${{ hashFiles('**/Cargo.lock') }}
 
+      - name: Login to DockerHub
+        if: (github.ref == 'refs/heads/master' || github.event_name == 'push') && github.repository == 'realaravinth/pages'
+        uses: docker/login-action@v1
+        with:
+          username: ${{ secrets.DOCKERHUB_USERNAME }}
+          password: ${{ secrets.DOCKERHUB_TOKEN }}
 
       - name: Install ${{ matrix.version }}
         uses: actions-rs/toolchain@v1
@@ -45,6 +51,9 @@ jobs:
       - name: run tests
         run: make test
 
+      - name: build and publish docker images
+        run: make docker-publish
+
       - name: generate documentation
         if: matrix.version == 'stable' && (github.repository == 'realaravinth/pages')
         run: make doc