map: 'by user' to add user-specific map links to embed

[synrg]

Similar to [p]taxon, pressing :hash: on a map embed should add a user's counts to the map which are links to the map for all included taxa by that user. Just as in that feature, also support a final 'total' count which is a link to all included taxa by all users in the embed.

[synrg]

To simply state this: just support the same 4 reaction buttons as we have on ,t and ,obs commands, and output the same table below the map embed. The only thing different would be the numbers themselves are produced by looking up multiple taxa (taxon_id=1,2,3). When you click any number, it opens to the observations on the web corresponding to all those taxa (for the user(s) / place(s) listed on that line of the table).