Describe the bug

When the input text contains full-width characters, the error location indicator (^) will point at the wrong character because it uses half-width spaces (U+20) only but it should instead match input characters' widths and use full-width spaces (U+3000) as well.

To Reproduce

Use any CJK characters or full-width version of latin scripts and intentionally create a grammar error. The indicator (^) will point at the wrong location.

Current and expected behavior shown here:

    raise UnexpectedCharacters(stream, i, text_line, text_column, {item.expect.name for item in to_scan},
lark.exceptions.UnexpectedCharacters: No terminal matches '古' in the current parser context, at line 2 col 6
1.菝葀：古代一種象徵祥瑞的草。《廣韻．入聲．末韻》：「菝：菝葀，瑞草。」
     ^  // using U+20 (current)
  　　　^  // using U+20 and U+3000 (expected)
Expected one of: 
	* LPAREN
	* I_LQUOTE