ci: coveralls workflow

.github/workflows/coverage.yml

@@ -0,0 +1,24 @@
+name: coveralls test coverage
+
+on:
+  push:
+    branches:
+      - main
+  pull_request:
+  release:
+    types:
+      - created
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v1
+      - uses: actions/setup-node@v1
+        with:
+          node-version: 16
+      - run: npm ci
+      - run: npm test
+      - uses: coverallsapp/github-action@master
+        with:
+          github-token: ${{ secrets.GITHUB_TOKEN }}