[MRG] Prepare for v2.1 release

[scaramallion]

Preparation for v2.1 release

Tasks

• Fix or feature added
• Documentation and examples updated (if relevant)
• Unit tests passing and coverage at 100% after adding fix/feature
• Type annotations updated and passing with mypy

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 100.00%. Comparing base (20993be) to head (979975f).
Report is 8 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##              main      #939   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           28        28           
  Lines         8703      8707    +4     
=========================================
+ Hits          8703      8707    +4     

Files	Coverage Δ
pynetdicom/_version.py	100.00% <100.00%> (ø)
pynetdicom/presentation.py	100.00% <100.00%> (ø)