Add Ruby head (3.5) to CI and deprecation warnings for frozen string …

…literals

.github/workflows/ruby.yml

@@ -19,7 +19,8 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        ruby-version: ['3.1', '3.2', '3.3']
+        ruby-version: ['3.1', '3.2', '3.3', '3.4', 'ruby-head']
+    continue-on-error: ${{ matrix.ruby-version == 'ruby-head' }}
 
     steps:
     - uses: actions/checkout@v4

Rakefile

@@ -26,6 +26,7 @@ task :test do
   Rake::TestTask.new do |t|
     t.libs << 'spec'
     t.test_files = FileList['spec/**/*_spec.rb']
+    t.ruby_opts = ['-W:deprecated']
     t.warning = true
     t.verbose = true
   end