LibJS: Report the start position of a token as its line column

Author: https://github.com/alimpfard
Commit: 7b54274ac5
Pull-request: https://github.com/SerenityOS/serenity/pull/1631
Reviewed-by: https://github.com/awesomekling

Libraries/LibJS/Lexer.cpp

@@ -391,7 +391,7 @@ Token Lexer::next()
         m_source.substring_view(trivia_start - 1, value_start - trivia_start),
         m_source.substring_view(value_start - 1, m_position - value_start),
         m_line_number,
-        m_line_column);
+        m_line_column - m_position + value_start);
 
     return m_current_token;
 }