ci: add Github action testing

Signed-off-by: Robin H. Johnson <robbat2@gentoo.org>

.github/workflows/test.yml

@@ -0,0 +1,38 @@
+name: Test
+
+on:
+  push:
+    branches: [ "master" ]
+  pull_request:
+    branches: [ "master" ]
+
+permissions:
+  contents: read
+
+jobs:
+  test:
+
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        ruby-version: ['2.7', '3.0', '3.1']
+
+    steps:
+    # Be careful adding changes here because the caching may be invalidated.
+    - uses: actions/checkout@v4
+    - name: Set up Ruby
+    # To automatically get bug fixes and new Ruby versions for ruby/setup-ruby,
+    # change this to (see https://github.com/ruby/setup-ruby#versioning):
+    # uses: ruby/setup-ruby@v1
+    # uses: ruby/setup-ruby@55283cc23133118229fd3f97f9336ee23a179fcf # v1.146.0
+      uses: ruby/setup-ruby@v1
+      with:
+        ruby-version: ${{ matrix.ruby-version }}
+        bundler-cache: true # runs 'bundle install' and caches installed gems automatically
+    # only add changes after this point.
+    - name: Run validate 
+      run: 'bundle exec rake validate'
+    - name: Run spec
+      run: 'SPEC_OPTS="--format documentation" bundle exec rake spec'
+    - name: Run lint
+      run: 'bundle exec rake lint'