chore: add ` R` git state

closes nvim-tree#723

fix: escape directory name before cd-ing (nvim-tree#725)

fix: filter also supports ext with other characters than words

fix: lsp diagnostics user autocmd setup

fix: remove lsp icons for loading in config

fix(colors): link signcolumn and normalnc to nvimtreenormal

chore: move help rendering in its own file

chore: complete the diagnostic setup migration

Colors groups and icons are now in diagnostics.lua. They are defined on
setup which allows an easier configuration and better documentation.
`lsp_diagnostics` boolean value has been moved into a table `diagnostics`
with `enable` and `icons` as properties.

fix: link normalNC and signcolumn to normal

fix: add normalNC color group

fixes nvim-tree#709