runtime(hlyank): promote the hlyank example to a package

[chrisbra]

related: #16866

[habamax]

It probably makes sense to add configuration for the function parameters.

...
var hlyank_hlgroup = get(g:, "hlyank_hlgroup", "IncSearch")
var hlyank_duration = get(g:, "hlyank_duration", 300)
var hlyank_invisual = get(g:, "hlyank_invisual", true)

augroup hlyank
  autocmd!
  autocmd TextYankPost * HighlightedYank(hlyank_hlgroup, hlyank_duration, hlyank_invisual)
augroup END

[habamax]

Looks good to me.