meta: stage a merge workflow

Adds a workflow that, on any push to master, will merge master to
release/next-js.

Presently targeted at another branch for testing.

.github/workflows/merge.yml

@@ -0,0 +1,18 @@
+name: merge
+on:
+  push:
+    branches:
+      - 'jt/merge-workflow'
+jobs:
+  merge-to-next-js:
+    runs-on: ubuntu-latest
+    name: "Merge master to release/next-js"
+    steps:
+      - uses: actions/checkout@v2
+      - uses: devmasx/merge-branch@v1.3.1
+        with:
+          type: now
+          from_branch: jt/test-merge-workflow
+          target_branch: jt/merge-workflow
+          github_token: ${{ github.token }}
+