update CI for changeset check (#12212)

Co-authored-by: chainchad <[email protected]>

.github/workflows/changeset.yml

@@ -0,0 +1,55 @@
+#
+# This action checks PRs to see if any changeset files were added in the PR core files were changed.
+# If none were, it will add a comment in the PR to run changeset command to generate a changeset file.
+#
+name: Changeset
+
+on: pull_request
+
+jobs:
+  changeset:
+    # For security reasons, GITHUB_TOKEN is read-only on forks, so we cannot leave comments on PRs.
+    # This check skips the job if it is detected we are running on a fork.
+    if: ${{ github.event.pull_request.head.repo.full_name == 'smartcontractkit/chainlink' }}
+    name: Changeset checker
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@b4ffde65f46336ab88eb53be808477a3936bae11 # v4.1.1
+      - uses: dorny/paths-filter@0bc4621a3135347011ad047f9ecf449bf72ce2bd # v3.0.0
+        id: files-changed
+        with:
+          token: ${{ secrets.GITHUB_TOKEN }}
+          filters: |
+            shared: &shared
+              - common/**
+              - plugins/**
+            core:
+              - *shared
+              - core/**
+            changeset:
+              - added: '.changeset/**'
+      - name: Make a comment
+        uses: unsplash/comment-on-pr@ffe8f97ccc63ce12c3c23c6885b169db67958d3b # v1.3.0
+        if: ${{ steps.files-changed.outputs.core == 'true' && steps.files-changed.outputs.changeset == 'false' }}
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        with:
+          msg: "I see you updated files related to core. Please run `pnpm changeset` to add a changeset."
+          check_for_duplicate_msg: true
+      - name: Check for new changeset
+        if: ${{ steps.files-changed.outputs.core == 'true' && steps.files-changed.outputs.changeset == 'false' }}
+        shell: bash
+        run: |
+          echo "Please run pnpm changeset to add a changeset."
+          exit 1
+      - name: Collect Metrics
+        if: always()
+        id: collect-gha-metrics
+        uses: smartcontractkit/push-gha-metrics-action@0281b09807758be1dcc41651e44e62b353808c47 # v2.1.0
+        with:
+          org-id: ${{ secrets.GRAFANA_INTERNAL_TENANT_ID }}
+          basic-auth: ${{ secrets.GRAFANA_INTERNAL_BASIC_AUTH }}
+          hostname: ${{ secrets.GRAFANA_INTERNAL_HOST }}
+          this-job-name: Changeset checker
+        continue-on-error: true