Add why gitmal to the readme

[jordandakota]

This is cool and probably helpful but clearly showing the problem statement it solves would help.

[antonmedv]

I guess everybody have they own problems =) I did this project just because I thought it was a cool idea.

I guess we can write something like: world domination.

[prologic]

The most obvious reason I can think of to add is to thwart these stupid incessant web crawling AI garbage bots that hammer your Gitea instance and it's poor littleSQLite database 😢