ci : Add github actions workflow to publish gem

Author: hoonti06

.github/workflows/publish-gem.yml

@@ -0,0 +1,20 @@
+name: Publish Gem
+
+on:
+  push:
+    tags:
+      - v*
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+
+      - name: Release Gem
+        if: contains(github.ref, 'refs/tags/v')
+        uses: cadwallion/publish-rubygems-action@master
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+          RUBYGEMS_API_KEY: ${{ secrets.RUBYGEMS_API_KEY }}
+          RELEASE_COMMAND: rake release

Rakefile

@@ -0,0 +1 @@
+require 'bundler/gem_tasks'