ci: add workflow for codecov

Signed-off-by: ktro2828 <[email protected]>

.github/workflows/codecov.yaml

@@ -0,0 +1,18 @@
+name: codecov
+
+on:
+  pull_request:
+    types: [opened]
+
+jobs:
+  codecov:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v3
+
+      - name: Upload coverage reports to Codecov
+        uses: codecov/[email protected]
+        with:
+          token: ${{ secrets.CODECOV_TOKEN }}