Release 0.4.0

[kmuehlbauer]

This is aimed to prepare for release 0.4.0

• [x] hook new cfradial1 export example notebook into usage.md
• [x] update history.md
• [x] set release date in CITATION.cff
• [x] updated README.md

[codecov[bot]]

Codecov Report

Merging #131 (a27df0b) into main (f46e5d1) will not change coverage. The diff coverage is n/a.

@@           Coverage Diff           @@
##             main     #131   +/-   ##
=======================================
  Coverage   88.31%   88.31%           
=======================================
  Files          20       20           
  Lines        3431     3431           
=======================================
  Hits         3030     3030           
  Misses        401      401           

Flag	Coverage Δ
unittests	88.31% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Files	Coverage Δ
xradar/io/export/cfradial1.py	91.66% <ø> (ø)

[kmuehlbauer]

@mgrover1 I'm going to get this released within the next hour. Please let me know, if there is anything more to do, thanks!