Improved performance of the text lexer.

Instead of highlighting non-whitespace characters one at a time, highlight whole ranges.

lexers/text.lua

@@ -7,4 +7,6 @@ local lex = lexer.new('text')
 
 lex:add_rule('whitespace', lexer.token(lexer.WHITESPACE, lexer.space^1))
 
+lex:add_rule('text', lexer.token(lexer.DEFAULT, (1 - lexer.space)^1))
+
 return lex