Improve fuzzy completion

[vindarel]

WIP

The fuzzy-match algorithm has good results (see tests, not yet ported, in https://github.com/vindarel/fuzzy-match),

  (lem/fuzzy-match:fuzzy-match "proj ws" (list of completion items) :key #'lem/completion-mode:completion-item-labe)
;; => "project-switch" item

the integration in Lem is not working properly, I have the visual glitch described in #1441

"proj sw" (with space) ->

I didn't find why yet, despite your indication.

[cianoc]

https://github.com/the-flx/cl-flx

Would it be simpler to use this, as it is pretty battle tested as algorithms go.