Add RFC 2822 serde module

[pitdicker]

Taking over from #1412.

Fixes #1292.

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 94.54545% with 3 lines in your changes are missing coverage. Please review.

Project coverage is 91.96%. Comparing base (0aa46dd) to head (b950bc4).

Files	Patch %	Lines
src/datetime/serde.rs	94.54%	3 Missing :warning:

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1477   +/-   ##
=======================================
  Coverage   91.95%   91.96%           
=======================================
  Files          40       40           
  Lines       18035    18090   +55     
=======================================
+ Hits        16584    16636   +52     
- Misses       1451     1454    +3     

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[pitdicker]

To be honest: while I opened this PR to take over, it is no priority for me. We can add an optional variant or review any time.