add CI for more RuboCop versions

Author: ashkulz

.github/workflows/checks.yml

@@ -11,13 +11,21 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        ruby: ['2.3', '2.4', '2.5', '2.6', '2.7', '3.0']
-        rubocop: ['0.63.1', '< 1.0']
+        ruby: ['2.4', '2.5', '2.6', '2.7', '3.0']
+        rubocop: ['0.63.1', '0.84.0', '0.85.0', '0.86.0', '0.87.0', '< 1.0']
+        include:
+          - ruby: '2.3'
+            rubocop: '0.63.1'
+          - ruby: '2.3'
+            rubocop: '0.81.0'
       fail-fast: false
     steps:
     - uses: actions/checkout@v2
-    - name: configure Gemfile.local
+    - name: use specific rubocop version
       run: echo "gem 'rubocop', '${{ matrix.rubocop }}'" > Gemfile.local
+    - name: use specific rubocop-ast version (if required)
+      if: matrix.rubocop == '0.84.0' || matrix.rubocop == '0.85.0' || matrix.rubocop == '0.85.1'
+      run: echo "gem 'rubocop-ast', '< 0.7.0'" >> Gemfile.local
     - uses: ruby/setup-ruby@v1
       with:
         ruby-version: ${{ matrix.ruby }}