build: test code coverage in CI

Author: AnzhiZhang

Diff for: .github/workflows/CI.yml

@@ -39,3 +39,9 @@ jobs:
       - uses: julia-actions/cache@v2
       - uses: julia-actions/julia-buildpkg@v1
       - uses: julia-actions/julia-runtest@v1
+
+      - uses: julia-actions/julia-processcoverage@v1
+      - name: Upload coverage reports to Codecov
+        uses: codecov/codecov-action@v4
+        with:
+          token: ${{ secrets.CODECOV_TOKEN }}