Automate gem publishing

.github/workflows/push_gem.yml

@@ -0,0 +1,25 @@
+on:
+  push:
+    tags:
+    - 'v*'
+
+jobs:
+  push:
+    name: Push gem to RubyGems.org
+    runs-on: ubuntu-latest
+
+    permissions:
+      id-token: write
+      contents: write
+
+    steps:
+    # Set up
+    - uses: actions/checkout@v4
+    - name: Set up Ruby
+      uses: ruby/setup-ruby@v1
+      with:
+        bundler-cache: true
+        ruby-version: "3.3"
+
+    # Release
+    - uses: rubygems/release-gem@v1