Add Positional Feature

[Daraan]

Resolves: #169

To also work for pydantic needs: #174, then also resolves: #165 (thats why latest tests) fail

Supports

from tap import Tap, Positional

class MyTap(Tap):
    positional_arg: Positional[int]
    positional_default: Positional[int] = 2
    positional_args: Positional[list[str]]

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Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 94.38%. Comparing base (2215ef5) to head (7199f92).
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Additional details and impacted files

@@            Coverage Diff             @@
##             main     #176      +/-   ##
==========================================
+ Coverage   94.18%   94.38%   +0.20%     
==========================================
  Files           4        4              
  Lines         757      784      +27     
==========================================
+ Hits          713      740      +27     
  Misses         44       44              

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[Daraan]

This avoids just an additional untrimmed space at the end of the help message if there is none; i.e. "(int, required) " -> "(int, required)"

[Daraan]

Ready for review :)

[martinjm97]

Thank you! This looks great! Sorry for the delay, we'll do our best to review this sizable PR soon.

--JK