Use upstream GH actions config

Updated with details specific to this project, like coverage

.github/workflows/main.yaml

@@ -1,47 +1,34 @@
-name: Main
+name: CI
 
-on: [push]
+on:
+  - push
+  - pull_request
 
 jobs:
-  vm-job:
+  build:
     runs-on: ubuntu-latest
-
-    # https://help.github.com/en/articles/workflow-syntax-for-github-actions#jobsjob_idstrategymatrix
     strategy:
       fail-fast: false
       matrix:
         ruby-version:
           - '3.0'
+          - '3.1'
           - '3.2'
           - '3.3'
           - head
 
     steps:
-    - uses: actions/checkout@v4
-
-    - name: Set up Ruby
-      uses: ruby/setup-ruby@v1
-      with:
-        ruby-version: ${{ matrix.ruby-version }}
-
-    - uses: actions/cache@v3
-      with:
-        path: vendor/bundle
-        key: ${{ runner.os }}-gems-${{ hashFiles('**/Gemfile.lock') }}
-        restore-keys: |
-          ${{ runner.os }}-gems-
-
-    - name: Bundle Install
-      run: |
-        gem install bundler
-        bundle install --jobs 4 --retry 3
-
-    - name: Run tests
-      run: |
-        COVERAGE=true bundle exec rspec
-    - name: Upload coverage results
-      uses: actions/upload-artifact@v4
-      if: always()
-      with:
-        name: coverage-report-ruby-${{ matrix.ruby-version }}
-        path: coverage
+      - uses: actions/checkout@v3
+      - name: Set up Ruby
+        uses: ruby/setup-ruby@v1
+        with:
+          ruby-version: ${{ matrix.ruby-version }}
+          bundler-cache: true
+      - name: Run tests
+        run: COVERAGE=true bundle exec rspec
+      - name: Upload coverage results
+        uses: actions/upload-artifact@v4
+        if: always()
+        with:
+          name: coverage-report-ruby-${{ matrix.ruby-version }}
+          path: coverage