map: build up map from individual taxon adds

[synrg]

Currently [p]map is a bit tricky in that if you typo even a single taxon, you won't get the intended map and then have to start over again. Therefore, similar to the recent observation counts support added to [p]taxon, it would be nice to add more taxa via reaction buttons.

• Unlike [p]taxon :hash: reaction which uses the iNat login id of the reacting user to update the taxon embed, we'd need some other mechanism for making additions, e.g.
  • Provide a reaction button for adding new taxa: :new:
    • When pressed, the user would be prompted to type a taxon in the usual way, with a taxon query, e.g. "chorus frogs"
    • If successful, the embed should be updated. And if not, an error should be shown.
  • Make the chart a numbered list to allow direct manipulation of the map entries by pressing number reactions (maybe just for removal?)