Move dependenbot auto-merge within the main workflow

This ensures auto-approve and auto-merge for dependabot only occurs when CI passes.

.github/workflows/main.yml

@@ -101,3 +101,22 @@ jobs:
         env:
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
           NPM_TOKEN: ${{ secrets.NPM_TOKEN }}
+
+  dependabot:
+    runs-on: ubuntu-latest
+    if: github.event.pull_request.user.login == 'dependabot[bot]' && github.repository == 'codama-idl/codama'
+    needs: [lint, tests]
+    permissions:
+      contents: write
+      pull-requests: write
+    steps:
+      - name: Auto-approve the PR
+        run: gh pr review --approve "$PR_URL"
+        env:
+          PR_URL: ${{ github.event.pull_request.html_url }}
+          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+      - name: Enable auto-merge
+        run: gh pr merge --auto --squash "$PR_URL"
+        env:
+          PR_URL: ${{ github.event.pull_request.html_url }}
+          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}