Support deserializing Python dataclass into structs / mappings

[davidhewitt]

Closes#93

[codecov]

Codecov Report

❌ Patch coverage is 92.06349% with 10 lines in your changes missing coverage. Please review.
✅ Project coverage is 84.48%. Comparing base (a444b75) to head (838b3cd).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
src/de.rs	92.06%	0 Missing and 10 partials ⚠️

Additional details and impacted files

@@ Coverage Diff @@## main #105 +/- ##
==========================================
+ Coverage 83.56% 84.48% +0.91% 
==========================================
Files 3 3 Lines 1065 1186 +121 Branches 1065 1186 +121 ==========================================
+ Hits 890 1002 +112 
Misses 118 118 - Partials 57 66 +9 

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