Create github ruby test action

.github/workflows/ruby.yml

@@ -0,0 +1,30 @@
+# This workflow will download a prebuilt Ruby version, install dependencies and run tests with Rake
+# For more information see: https://github.com/marketplace/actions/setup-ruby-jruby-and-truffleruby
+name: Ruby
+
+on:
+  push:
+    branches: [ "main" ]
+  pull_request:
+    branches: [ "main" ]
+
+permissions:
+  contents: read
+
+jobs:
+  test:
+
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        ruby-version: [ '3.1', '3.2', '3.3' ]
+
+    steps:
+    - uses: actions/checkout@v4
+    - name: Set up Ruby
+      uses: ruby/setup-ruby@v1
+      with:
+        ruby-version: ${{ matrix.ruby-version }}
+        bundler-cache: true # runs 'bundle install' and caches installed gems automatically
+    - name: Run tests
+      run: bundle exec rake

attributed-string.gemspec

@@ -18,5 +18,5 @@ Gem::Specification.new do |spec|
   spec.metadata["homepage_uri"] = "https://github.com/instruct-rb/attributed-string"
 
 
-  spec.required_ruby_version = ">= 3.2.3"
+  spec.required_ruby_version = ">= 3.1"
 end