Add release job.

Author: kporras07

.github/workflows/ci.yml

@@ -83,3 +83,22 @@ jobs:
         run: chmod +x terminus.phar
       - name: Functional Tests
         run: composer functional
+
+  release:
+    runs-on: ubuntu-latest
+    name: Release
+    container:
+      image: quay.io/pantheon-public/php-ci:1.x
+    needs: [functional]
+    if: ${{ startsWith(github.ref, 'refs/tags/') }}
+    steps:
+      - name: Download terminus.phar as artifact
+        uses: actions/download-artifact@v2
+        with:
+          name: terminus-phar
+      - name: Release
+        uses: softprops/action-gh-release@v1
+        with:
+          files: terminus.phar
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}