Problem: filetype: rasi files are not recognized
Solution: regonize '*.rasi' files as rasi filetype,
include a filetype and syntax plugin
(Pierrick Guillaume)
ported from: https://github.com/Fymyte/rasi.vimcloses: vim/vim#14821280e5b13ca
Co-authored-by: Pierrick Guillaume <pierguill@gmail.com>