docs: Make `jj log -T builtin_log_redacted` more visible for bug reports & other issues

Ideally we update the GH bug report Template also to mention it.

This is a good task if you want to start to contribute to the project. The same issue also exists for the redacted operation log template, see builting_op_log_redacted.

What I mean by making it more visible:

• Having an example output of it on the website and a general description of its use.
• The docs for jj log also should mention the template explicitly for sharing