message: Update README as codecov action v1 is deprecated.
  See also:
diff: @@ -425,7 +425,7 @@ jobs:
  cargo +nightly tarpaulin --verbose --all-features --workspace --timeout 120 --out Xml
  - name: Upload to codecov.io
  - uses: codecov/codecov-action@v1
  + uses: codecov/codecov-action@v2
  with:
  # token: ${{secrets.CODECOV_TOKEN}} # not required for public repos
  fail_ci_if_error: true
  