Move CI to GitHub actions

.github/workflows/test.yml

@@ -0,0 +1,18 @@
+name: Test
+on: [push, pull_request]
+jobs:
+  test:
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [ubuntu-latest, macos-latest]
+        # Due to https://github.com/actions/runner/issues/849, we have to use quotes for '3.0'
+        ruby: ['2.7', '3.0', '3.1', '3.2', head, jruby, jruby-head, truffleruby, truffleruby-head]
+    runs-on: ${{ matrix.os }}
+    steps:
+      - uses: actions/checkout@v4
+      - uses: ruby/setup-ruby@v1
+        with:
+          ruby-version: ${{ matrix.ruby }}
+          bundler-cache: true # runs 'bundle install' and caches installed gems automatically
+      - run: bundle exec rake

.ruby-version

@@ -1 +1 @@
-2.6.4
+3.2.0

rack-brotli.gemspec

@@ -26,7 +26,7 @@ Gem::Specification.new do |s|
 
   s.extra_rdoc_files = %w[README.md COPYING]
 
-  s.add_runtime_dependency 'rack', '>= 1.4'
+  s.add_runtime_dependency 'rack', '>= 1.4', '< 3'
   s.add_runtime_dependency 'brotli', '>= 0.1.7'
 
   s.add_development_dependency 'bundler'