Issue title: Improvement - when middle mouse button pressed, switch temporarily to the Hand function
 Issue body: This would make navigation in the document possible just with the mouse.
Thanks.
 Comments: 
 Comment 0: Thanks for the report @vrozkovec, this is good idea, we'll keep it in mind for next releases 😉 

{'source': 'GithubIssues', 'repo_name_with_owner': 'avocode/avocode', 'issue_id': 174050652, 'repo_stars': 227.0}