Fix aria selectors, space handling inside strings and improve error reporting

[borela]

Group aria edge case

Fixes:

# Before
group-aria-[disabled=false]: opacity-100

# Now
group-aria-[disabled=false]:opacity-100

Prevent unnecessary escapes in JSX

JSX strings don't support backslash escaping at all, and they treat them as literal characters; the extra escape added was making it harder to read.

Improve error reporting

Error messages now show the place where parsing failed.

Adjust readmes

The parser allows spaces instead of _ in all classes, and the readmes were not showing this in all scenarios.