Add _geoPolygon and _geojson documentation

[guimachiavelli]

Fixes EXP-246

[Strift]

Hey,

It appears the 4th parameter of the _geoRadius filter, resolution is not documented.

Do we want to mention it? At least in code samples?

[guimachiavelli]

I was honestly not aware of its existence and can't find any references to it on Notion/specs. Can you point me to a resource mentioning it?

EDIT

I checked this with @irevoire. Apparently resolution was not meant to be accessible for users, but it was implemented that way due to miscommunication. At this point it's too late to roll it back. I'm waiting for the full usage info, and will document it ASAP.

Thanks for pointing it out, @Strift, nice catch!