feat(danger): Enable Danger through github actions

Use github actions to run danger

Signed-off-by: Jason Field <jason@avon-lea.co.uk>

.github/workflows/danger.yml

+name: danger
+
+on:
+  pull_request_target:
+    types: [assigned, opened, synchronize, reopened]
+    branches-ignore:
+      - main
+
+jobs:
+  danger:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Check out code
+        uses: actions/checkout@v2
+      - name: Run Danger
+        uses: actionshub/danger-rb@main
+        env:
+          DANGER_GITHUB_API_TOKEN: ${{ secrets.GITHUB_TOKEN }}