[WO-601] Fix parsing error with empty literals in the end of lists

If a list `(...)` ended with an empty literal then the enclosing parenthesis was considered as part of the literal and this broke whatever came after

The change includes a lot of code formatting changes that can be ignored, the relevant changes are:

  * [updated parser code](https://github.com/whiteout-io/imap-handler/blob/b4d32cde3ca8291c80bfe5f585bee8c0e5c68782/src/imap-parser.js#L520-L528)
  * [test that failed with the old parser](https://github.com/whiteout-io/imap-handler/blob/b4d32cde3ca8291c80bfe5f585bee8c0e5c68782/test/imap-parser-unit.js#L292-L299)