[docs] Document trace.log contains debug level information

[ttddyy]

While configuring JReleaser, I wanted to get a more detailed log to see what is really happening under the hood when something went wrong.

I found trace.log has the debug level logs almost at the end I configured the JReleaser to the project.

It would be nice to call out in the documentation that trace.log is available for debugging. So that, users would aware of how to debug release failures.

[aalmiray]

There's a mention of trace.log at https://jreleaser.org/guide/latest/checklist.html However, these 2 files could also be mentioned in the Quickstart pages, and perhaps other places as well.