Auto assign /me in default MR template

What does this MR do and why?

Save a few clicks as most new MRs should be assigned to their authors.

Screenshots or screen recordings

Allows me to forget to click here:

How to set up and validate locally

NA

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.