[Feature request] Add syntax highlight for diff view

[hamflx]

related to #358 , but https://github.com/dandavison/delta has wrong highlight when diffing .vue files.

my draft implementation:

delta:

my impletation diffs the whole file twice, so the performance may be affected

@extrawurst i'll create a pr for it if this solution is acceptable

[adsick]

Bump. Almost a year has passed.