create coverage action

.github/workflows/coverage-diff.yml

@@ -0,0 +1,32 @@
+name: Coverage Diff
+
+on:
+  push:
+    branches:
+      - master
+  pull_request:
+    types:
+      - opened
+      - synchronize
+      - reopened
+      - ready_for_review
+    branches:
+      - master
+
+jobs:
+  test:
+    name: Coverage Diff
+    runs-on: windows-latest
+
+    steps:
+      - uses: actions/checkout@v2
+      - uses: actions/setup-node@v2
+        with:
+          node-version: 16
+          cache: npm
+      - run: npm install
+      - run: npm run test
+      - name: Coverage Diff
+        uses: greatwizard/coverage-diff-action@v1
+        with:
+          github-token: ${{ secrets.GITHUB_TOKEN }}