[Python] Advanced string formatting

[ome9ax]

I added the native 🐍 Python string formatting for datetime type.
This should cover #20 feature request from @aroder.

[codecov-commenter]

Codecov Report

Merging #31 (28ce784) into main (427cc6a) will not change coverage.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##              main       #31   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            3         3           
  Lines          185       191    +6     
  Branches        37        37           
=========================================
+ Hits           185       191    +6     

Flag	Coverage Δ
unittests	100.00% <100.00%> (ø)

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Impacted Files	Coverage Δ
target_s3_jsonl/__init__.py	100.00% <100.00%> (ø)

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