fix(highlights): Fix support for Multibyte characters

[LamprosPitsillos]

Trying to fix support for multibyte characters (utf8) as they don't get printed correctly. Having trouble with nil indexing inside the ts() function

[Sam-programs]

Having trouble with nil indexing inside the ts() function

Tree-sitter functions return byte positions, but ret has utf8-character positions. Using utf8 positions will also cause issues in draw_cmdline, because the cursor logic expects byte positions.