MRU file management improvement.

[ubaldot]

I noticed that the plugin relies on an external MRU file.

Perhaps an improvement could be done by exploitation of v:oldfiles instead of relying on external files.

That is, the following code snippet generate a list of recently opened files:

vim9script

var mru_list =  copy(v:oldfiles)->filter((_, val) => filereadable(expand(val)))
echom mru_list