Add TOTP field for the Field class

[edif2008]

Starting with Connect 1.4.0 we introduced the capability to get the totp value through Connect. Now the SDK supports that as well.

[codecov-commenter]

Codecov Report

Merging #33 (aeb8a42) into main (678d607) will increase coverage by 0.14%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main      #33      +/-   ##
==========================================
+ Coverage   76.08%   76.22%   +0.14%     
==========================================
  Files          21       21              
  Lines        1597     1607      +10     
==========================================
+ Hits         1215     1225      +10     
  Misses        382      382              

Impacted Files	Coverage Δ
src/onepasswordconnectsdk/models/field.py	82.35% <100.00%> (+1.44%)	⬆️
src/tests/test_client_items.py	100.00% <100.00%> (ø)

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