Kubo/Boxo: pre PR signal that a contributor needs to run "go mod tidy"

[BigLep]

Done Criteria

Before a contributor makes a PR to Boxo or Kubo they should have indication if their PR will fail CI checks due to go mod tidy checks.

Why Important

1. This trips up most new contributors to the codebase
2. Maintainers end up copy/pasting messages like https://github.com/ipfs/kubo/pull/9787#issuecomment-1532313618

Notes

1. We're not going to run mutating code by default, but during the make/build process we can highlight the issue and point someone to the steps they need to take.