Auto generated links should also have title

[Padeanu]

Hello, at this point, auto generated links only contain rel, type and href.

stac-fastapi-pgstac/stac_fastapi/pgstac/models/links.py

Line 78 in baac642

def link_self(self) -> Dict:

It would be nice that in future versions, to also contain a title.

{
     "rel": "root",
     "type": "application/json",
     "href": "http://127.0.0.1:8000/app/api"
}

to

{
     "rel": "root",
     "type": "application/json",
     "title": "App Root API",
     "href": "http://127.0.0.1:8000/app/api"
}

Maybe it's possible and i'm missing something? Otherwise i can contribute with a PR.