Include 'title' in href when the target link's title can be easily discerned

[cholmes]

There's going to be one minor change for STAC 1.0.0, that's just a small recommendation, but it'd be great to implement in pystac.

See radiantearth/stac-spec#1133

I don't think we need to try to always fill out the title, but when it's easy for PySTAC, like since it's also writing out the title of the target entity (item, catalog, collection) then it'd be good to include it. Perhaps we also could have some nudge to encourage people to include titles...

This was originally thought about as an 'option' in stactools, see stac-utils/stactools#22 but since it's getting in the spec as a recommendation it probably makes sense to just try to do it by default in pystac.