chore: add workflow to release gem

Author: bethesque

.github/workflows/release_gem.yml

@@ -0,0 +1,24 @@
+name: Release gem
+
+on:
+  push:
+    tags:
+      - release
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v2
+      with:
+        fetch-depth: 0
+    - uses: pact-foundation/release-gem@v0.0.5
+      env:
+        GEM_HOST_API_KEY: '${{ secrets.RUBYGEMS_API_KEY }}'
+        GITHUB_TOKEN: '${{ secrets.GITHUB_TOKEN }}'
+    # - name: Trigger release of pact-cli Docker image
+    #   uses: peter-evans/repository-dispatch@v1
+    #   with:
+    #     token: ${{ secrets.GHTOKENFORPACTCLIRELEASE }}
+    #     repository: pact-foundation/pact-ruby-cli
+    #     event-type: gem-released