Add an indication that GeoPolars isn't production-ready, and its dev is on-hold

[DeflateAwning]

GeoPolars, linked in the Rust section, will be awesome when its development resumes (or an alternative comes along).

At the top of its readme, there an update that reads:

Update (August 2024): GeoPolars is pola-rs/polars#1830 (comment) on Polars supporting pola-rs/polars#9112, which would allow GeoPolars to persist geometry type information and coordinate reference system (CRS) metadata. It's not feasible to create a geopolars.GeoDataFrame as a subclass of a polars.DataFrame (similar to how the geopandas.GeoDataFrame is a subclass of pandas.DataFrame) because polars explicitly pola-rs/polars#2846 (comment). See geopolars/geopolars#240.

With this, I would suggest adding an indication that it's pre-alpha and not in active development.

I would suggest removing it from the list, but I think it's best to leave it on the list to indicate that it's a project that exists (and the only one of its kind currently), but that it's not the current Polars direction.

[ddotta]

Thanks @DeflateAwning for this issue.
You're right, I'll just add the pre-alpha indication