Visualization for scope types

[pokey]

• [x] add a command "show scopes <scopeType>" eg "show scopes funk"
• [x] will highlight all scopes on screen using semi-transparent background to make nesting visible
• [ ] could also do "show scope hierarchy" which would show hierarchy of all scope types containing given scope
• [x] note these are cursorless scope types, not raw tree-sitter scope types
• [ ] could use this one for keyboard version and do it as the user types
• [x] need to think of good api for scope types so that we can get this information easily
• [ ] could have "hint scopes <scopeType>" to make it disappear after a couple seconds, or after next command
• [x] might be useful to map to a noise? not by default
• [ ] think about making it nonintrusive enough to leave on for a while
• [x] update as you scroll?