This commit allows using the <semicolon> expansion in commands, instead
of `\;`.
It makes commands look more elegant, and prevents new-comers from
falling into the trap of using <a-;> without escaping the semicolon.
* Adapt the char literal highlighter from c-family.kak
* Fix line comment adjacent to char literal not being highlighted
* Fix single quote terminating a double quote string
* Fix keywords in comments being highlighted
* Highlight Nim's escape sequences for strings
* Highlight common comment tags
* Add on/off to the highlighted boolean values
* Remove redundant regex highlighter for comments
* Fix autoindent indenting lines more than it should
Before:
```nim
type
MyType = tuple
myint: int # This line needs to be indented manually
```
After:
```nim
type
MyType = tuple
myint: int # Lines after 'tuple' are now indented automatically
```
