Add support for filtering to note browser

[Furkanzmc]

This should work similar to how vim-dirvish handles filtering so it's easy to sort or filter notes based on simple regular expressions.

[Furkanzmc]

I don't think a separate feature for this is necessary. :help :g already works in the note browser buffer and sorting can be achieved in a similar way as well. There's a new wiki entry for sorting, and maybe one day I'll add one for filtering as well.