Added workflows for GitHub Actions.

.github/workflows/macos.yml

@@ -0,0 +1,15 @@
+name: macos
+
+on: [push]
+
+jobs:
+  build:
+    runs-on: macos-latest
+    steps:
+    - uses: actions/checkout@master
+    - name: Install dependencies
+      run: |
+        gem install bundler --no-document
+        bundle install
+    - name: Run test
+      run: rake

.github/workflows/ubuntu-rvm.yml

@@ -0,0 +1,29 @@
+name: ubuntu-rvm
+
+on: [push]
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        ruby: [ 'jruby-9.2.6.0', 'jruby-9.1.17.0', 'ruby-head' ]
+    steps:
+    - uses: actions/checkout@master
+    - name: Set up RVM
+      run: |
+        curl -sSL https://get.rvm.io | bash
+    - name: Set up Ruby
+      run: |
+        source $HOME/.rvm/scripts/rvm
+        rvm install ${{ matrix.ruby }} --binary
+        rvm --default use ${{ matrix.ruby }}
+    - name: Install dependencies
+      run: |
+        source $HOME/.rvm/scripts/rvm
+        gem install bundler --no-document
+        bundle install
+    - name: Run test
+      run: |
+        source $HOME/.rvm/scripts/rvm
+        rake

.github/workflows/ubuntu.yml

@@ -0,0 +1,22 @@
+name: ubuntu
+
+on: [push]
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        ruby: [ '2.6.x', '2.5.x', '2.4.x', '2.3.x' ]
+    steps:
+    - uses: actions/checkout@master
+    - name: Set up Ruby
+      uses: actions/setup-ruby@v1
+      with:
+        version: ${{ matrix.ruby }}
+    - name: Install dependencies
+      run: |
+        gem install bundler --no-document
+        bundle install
+    - name: Run test
+      run: rake

.github/workflows/windows.yml

@@ -0,0 +1,22 @@
+name: windows
+
+on: [push]
+
+jobs:
+  build:
+    runs-on: windows-latest
+    strategy:
+      matrix:
+        ruby: [ '2.6.x', '2.5.x', '2.4.x' ]
+    steps:
+    - uses: actions/checkout@master
+    - name: Set up Ruby
+      uses: actions/setup-ruby@v1
+      with:
+        version: ${{ matrix.ruby }}
+    - name: Set up Bundler
+      run: gem install bundler --no-document
+    - name: Install dependencies
+      run: bundle install
+    - name: Run test
+      run: rake

Gemfile

@@ -1,3 +1,12 @@
 source 'https://rubygems.org'
 
 gemspec
+
+group :development do
+  gem "rake"
+  gem "racc", "> 1.4.10"
+  gem "kpeg"
+  gem "test-unit"
+  gem "minitest" # for test_rdoc_rubygems_hook.rb
+  gem "rubocop"
+end

rdoc.gemspec

@@ -53,10 +53,4 @@ RDoc includes the +rdoc+ and +ri+ tools for generating and displaying documentat
   s.required_ruby_version = Gem::Requirement.new(">= 2.2.2")
   s.rubygems_version = "2.5.2"
   s.required_rubygems_version = Gem::Requirement.new(">= 2.2")
-
-  s.add_development_dependency("rake")
-  s.add_development_dependency("racc", "> 1.4.10")
-  s.add_development_dependency("kpeg")
-  s.add_development_dependency("minitest", "~> 5")
-  s.add_development_dependency("rubocop")
 end