Update 'creating alt geometries` doc

[stepps00]

https://github.com/whosonfirst/whosonfirst-cookbook/blob/master/how_to/creating_alt_geometries.md#what-rules-must-alt-geometries-follow

This doc needs additional info about how to create alt geometries (specifically, updating the properties list in the doc). More info here:

https://github.com/whosonfirst-data/whosonfirst-data/issues/1804

[stepps00]

fixed in: https://github.com/whosonfirst/whosonfirst-cookbook/commit/5fa50c0869f89be9dfb4f1208066bdc6d7386808 and https://github.com/whosonfirst/whosonfirst-cookbook/commit/01ee41f1b5a426b717cf5512ae0667a061576733