add boundary=marker (historic=boundary_stone is already in presets)

[jidanni]

https://wiki.openstreetmap.org/wiki/Tag:boundary%3Dmarker could even be a remote corner of a ranch. A very important point to map. However not a historic=boundary_stone. Therefore iD needs to be more flexible.

[bryceco]

Okay, but don't close as a duplicate. That only applies when someone else already reported it.

This bug was moved from openstreetmap/iD#8509

[dheeraj12347]

I’d like to work on this: plan is to add a boundary=marker preset (modeled on historic=boundary_stone) using the combinations from the wiki page.