vifm is removed in favour of nnn, with the keybindings in nvim being
changed. TODO: improve the colorscheme of `nnn` to match `ls`.
All nvim plugins that were responsible for language syntax highlighting
are removed in favour of treesitter[1], a syntax highlighter that parses
AST instead of being regex-based. This is still experimental, but my
tests so far have not encountered any issues.
1) https://github.com/nvim-treesitter/nvim-treesitter
