Fix character brackets behave like normal code

[xiaoyu2006]

Fixes #80.

Original code misunderstood schematic differences between "constant.character.racket" and "string.quoted.single.racket":

• string.quoted.single.* usually means 'sometext' form
• string.quoted.double.* usually means "sometext" form
• constant.character.* usually represents "\someescaped" highlighting form

In this specific context #\char falls into the first category.

[jryans]

I'll aim to release a new version with this sometime this week hopefully.