[Parquet-raster] Allowed URL schemes here

[jiayuasu]

          Putting some obvious schemes here. Open to new ideas!

Originally posted by @jiayuasu in #259 (comment)

[paleolimbot]

FWIW Arrow just had a similar discussion around Flight endpoints...we opted to go for http[s] only because the URL schemes for other protocols are not strictly defined (notably, s3:// is reinvented everywhere). I'm not sure what types of URLs appear in STAC but perhaps they have language we can steal?