Update CI GitHub workflow

Allow CI to be skipped with `[skip rspec]` in the pull request
description.

.github/workflows/ci.yml

@@ -13,10 +13,34 @@ permissions:
   contents: read
 
 jobs:
+  check:
+    runs-on: ubuntu-latest
+
+    outputs:
+      skip_rspec: ${{ steps.skip.outputs.skip_rspec }}
+
+    env:
+      GH_TOKEN: ${{ github.token }}
+
+    steps:
+    - name: Check for [skip rspec]
+      id: skip
+      run: |
+        PR_DESCRIPTION=$(gh pr view https://github.com/${{ github.repository }}/pull/${{ github.event.pull_request.number }} --json body -q '.body')
+        if echo "$PR_DESCRIPTION" | grep -q "\[skip rspec\]"; then
+          echo "Skip RSpec found in PR description. Passing the action."
+          echo "skip_rspec=true" >> $GITHUB_OUTPUT
+        else
+          echo "skip_rspec=false" >> $GITHUB_OUTPUT
+        fi
+
   rspec:
     name: Ruby ${{ matrix.ruby }} / PostgreSQL ${{ matrix.postgres }}
     runs-on: ubuntu-20.04
 
+    needs: check
+    if: needs.check.outputs.skip_rspec == 'false'
+
     permissions:
       checks: write # for coverallsapp/github-action to create new checks