docs: Add guidance on adding new indirect/direct imports. #1913
Description
As per https://cloud-native.slack.com/archives/C01AUBA4PFE/p1762272462094259?thread_ts=1762169496.875849&cid=C01AUBA4PFE there is a lot to understand when it comes to adding new dependencies to client_golang (any stable, highly adopted lib).
Things to cover:
- Vendoring vs new dep
- Using unstable dep
- Topic of indirect deps
- Deps in tests & examples vs prod code