Release candidate 0.11.0

[danielhuppmann]

This PR

• updates the release notes with a highlights section
• implements a few minor formatting fixes in the docstrings and stale references to the master branch (renamed to main)

[codecov]

Codecov Report

Merging #516 (7e6fcac) into main (8b0c538) will not change coverage.
The diff coverage is n/a.

@@          Coverage Diff          @@
##            main    #516   +/-   ##
=====================================
  Coverage   93.1%   93.1%           
=====================================
  Files         43      43           
  Lines       4932    4932           
=====================================
  Hits        4594    4594           
  Misses       338     338           

Impacted Files	Coverage Δ
pyam/core.py	92.4% <ø> (ø)
pyam/unfccc.py	89.7% <ø> (ø)

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[danielhuppmann]

merging after publishing on test.pypi.org