Link to troubleshooting docs when src campaign apply|preview fails
Created by: mrnugget
This fixes https://github.com/sourcegraph/sourcegraph/issues/17259, but contrary to what I stated in the original ticket, I think it makes more sense to always link to these docs.
Why?
- It's two lines. It doesn't hurt.
- It's really tricky to find out exactly when to link to the docs and when not. Especially since running the steps could result in an error that could be fixed through the troubleshooting guide (example: broken docker setup).