feat(lexer): finished

src/lexer/lexer.h

@@ -30,6 +30,7 @@ char *new_token(char *begin, ssize_t size);
  *         If it is, it calls stream_read() from IO_backend,
  *         and sets [remaing_chars].
  *         If not, it starts from the end of the last token.
+ *         Also trims left blanks before returning.
  *
  * @return: char* stream from which we tokenise.
  */