v2.1

The bug fixed version for https://github.com/FrLars21/ZoteroCitationCountsManager/releases/tag/v2.0.

• fix bug with any action in annotation or tags causing an auto fetch citation number.
• fix bug with servel arXiv paper cannot fetch DOI or citation number.
• add icons in manu and installation page.

Full Changelog: https://github.com/BugBubbles/ZoteroCitationCountsManager/commits/v2.1