Allow jumping to a letter/word in the visible viewport

[ffpetrovic]

the ace jump extension allows this in VSCode, and it's really unfortunate there's no such functionality in Zed. I also find that it's too much to migrate muscle memory to VIM's movement just to get VIM sneak. This should be possible without integrating into the world of VIM.

AFAIK "overlays" aren't yet possible in Zed, but maybe they're not necessary for this feature?