Enable code coverage

Author: jacebrowning

.github/workflows/main.yml

@@ -41,8 +41,8 @@ jobs:
     - name: Run Demo
       run: make demo
 
-    # TODO: Add code coverage
-    # - name: Upload coverage
-    #   uses: codecov/codecov-action@v1
-    #   with:
-    #     fail_ci_if_error: true
+    - name: Upload coverage
+      uses: codecov/codecov-action@v4
+      with:
+        fail_ci_if_error: true
+        token: ${{ secrets.CODECOV_TOKEN }}