Migrate to codecov-action@v4 (#111)

Author: vers-one

.github/workflows/test.yml

@@ -25,6 +25,8 @@ jobs:
       - name: Run unit tests
         run: dotnet test Source\VersOne.Epub.Test --filter Unit --no-restore --collect:"XPlat Code Coverage" --settings Source\VersOne.Epub.Test\coverlet.runsettings
       - name: Upload code coverage result to Codecov
-        uses: codecov/codecov-action@v3
+        uses: codecov/codecov-action@v4
+        with:
+          token: ${{ secrets.CODECOV_TOKEN }}
       - name: Run integration tests
         run: dotnet test Source\VersOne.Epub.Test --filter Integration --no-restore