Allow `EnableHLXYZ` / `DisableHLXYZ` to work buffer-locally

[hinell]

Is your feature request related to a problem? Please describe.
Currently the EnableHLXYZ / DisableHLXYZ commands enable/disable hlchunk globally. No way to disable/enable hlchunk per given buffer.

Describe the solution you'd like
Expose an API that would allow disabling/enabling hlchunk per buffer. E.g.:

require("hlchunk").disable({ bufnr = bunfr }) -- disable every mod of hlchunk
require("hlchunk.mods.chunk").disable({ bufnr = bunfr }) 
require("hlchunk.mods.indent").disable({ bufnr = bunfr }) 
require("hlchunk.line_num.indent").disable({ bufnr = bunfr }) 

Describe alternatives you've considered
There are no alternatives. Docs say nothing on that.

Additional context
In big files it's desirable to turn off highlighting and various plugins in associated buffers.