Upgrade CI rubies, upgrade Rubocop and move it to separate CI job

.github/workflows/lint.yaml

@@ -0,0 +1,32 @@
+name: Lint Ruby
+
+on:
+  push:
+    branches:
+      - master
+    paths:
+      - "gemfiles/*"
+      - "Gemfile"
+      - "**/*.rb"
+      - "**/*.gemspec"
+      - ".github/workflows/lint.yml"
+  pull_request:
+    paths:
+      - "gemfiles/*"
+      - "Gemfile"
+      - "**/*.rb"
+      - "**/*.gemspec"
+      - ".github/workflows/lint.yml"
+
+jobs:
+  rubocop:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+      - uses: ruby/setup-ruby@v1
+        with:
+          ruby-version: 3.2
+          bundler-cache: true
+      - name: Lint Ruby code with RuboCop
+        run: |
+          bundle exec rubocop

.github/workflows/test.yml

@@ -17,31 +17,15 @@ jobs:
       fail-fast: false
       matrix:
         include:
-          - ruby: 3.0
-          - ruby: 2.7
-          - ruby: 2.6
-          - ruby: 2.5
-    container:
-      image: ruby:${{ matrix.ruby }}
-      env:
-        CI: true
+          - ruby: "3.2"
+          - ruby: "3.1"
+          - ruby: "3.0"
+          - ruby: "2.7"
     steps:
-      - uses: actions/checkout@v2
-      - uses: actions/cache@v2
+      - uses: actions/checkout@v3
+      - uses: ruby/setup-ruby@v1
         with:
-          path: vendor/bundle
-          key: bundle-${{ matrix.ruby }}-${{ hashFiles('**/*.gemspec') }}-${{ hashFiles('**/Gemfile') }}
-          restore-keys: |
-            bundle-${{ matrix.ruby }}-${{ hashFiles('**/*.gemspec') }}-${{ hashFiles('**/Gemfile') }}
-            bundle-${{ matrix.ruby }}-
-      - name: Upgrade Bundler to 2.0 (for older Rubies)
-        run: gem install bundler -v '~> 2.0'
-      - name: Bundle install
-        run: |
-          bundle config path vendor/bundle
-          bundle install
-          bundle update
-      - name: Run Rubocop
-        run: bundle exec rubocop
+          ruby-version: ${{ matrix.ruby }}
+          bundler-cache: true
       - name: Run RSpec
         run: bundle exec rspec

Gemfile

@@ -7,6 +7,6 @@ gemspec
 
 gem 'byebug'
 gem 'rack'
-gem 'rake', '~> 12.0'
+gem 'rake', '~> 13.0'
 gem 'rspec', '~> 3.0'
-gem 'rubocop', '~> 0.81.0'
+gem 'rubocop', '~> 1.0'