Bibtex Encoder disregards `editor` key for use as Author with editor role when importing Bibtex content

Problem/Motivation
When trying to import Publications, Bibtex does not recognize these values editor = {Editor One and Editor Two} to be used as Authors and does nothing with them and passes them along as a string.
While for authors it separates multiple entries into different arrays.
We should do the same for for editor entries if found in bibtex file.
I found this is due to BibtexParser::parse_string library as it only cares for authors.
This, in turn, leads to the omission of Editors all together when the Reference entity is normalized. No new contributors are created which are placed in editor key which should be actually created and assigned editor roles.

Proposed resolution
Use \Drupal\bibcite_bibtex\Encoder\BibtexEncoder::processEntries to implement Workaround about some things in BibtexParser library to care for `Editor` key in array.
Make changes in \Drupal\bibcite_entity\Normalizer\ReferenceNormalizerBase::denormalize to care for editor role as well, right now it only supports Author role while importing Bibtex content.