Add codecov

Author: casmith

.github/workflows/release.yml

@@ -19,4 +19,13 @@ jobs:
       - run: npm test
       - run: npm run release
         env:
-          GITHUB_TOKEN: ${{ secrets.GH_TOKEN }}
+          GITHUB_TOKEN: ${{ secrets.GH_TOKEN }}
+      
+      - uses: codecov/codecov-action@v2
+        with:
+          token: ${{ secrets.CODECOV_TOKEN }} # not required for public repos
+          #files: ./coverage1.xml,./coverage2.xml # optional
+          flags: unittests # optional
+          name: codecov-umbrella # optional
+          fail_ci_if_error: true # optional (default = false)
+          verbose: true # optional (default = false)