Add right-click option to handles to scroll the tag list to view the tag with that handle

[WeaverSong]

It's very easy to find a tag that needs to be edited visually, but inconvenient to find it in the tag list for when the handles are insufficient.

[Mew Pur Pur]

I approve, but I'm unsure of the implementation. I was trying to do this at one point by trying to make it automatically scroll. It didn't work precisely enough for some reason. Nowadays, there's a function for finding the rect of a tag editor somewhere, so it might work if we use that.

[Mew Pur Pur]

Solved by #719