- Adds the rainbow_csv plugin to improve CSV file support.
- Sets mutliple filetypes for markdown plugins (`pandoc`, `markdown`).
- `mkdnflow`.
- `markdownpreview`.
- `marksman` language server (but it doesn't work for pandoc
filetype).
- Sets folding level to 1 to fold from the level 2 headings.
- Sets the python virtualenv as python3 provider.
- Updates the English dictionnaries.
Co-Authored-by: iGor milhit <igor@milhit.ch>