feat: add compact= arg to for fmt_currency()

[rich-iannone]

This PR adds the compact= parameter to fmt_currency(), so that values such as $12,345 can render as $12.34K. The behavior of compact= here is the same as in other formatters like fmt_number() and fmt_integer().

Here's an example of its use:

from great_tables import GT, exibble

GT(exibble[["num", "currency"]]).fmt_currency(columns="currency", scale_by=1000, compact=True)

Fixes: #649

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 91.18%. Comparing base (33c7be9) to head (76cdba4).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #664   +/-   ##
=======================================
  Coverage   91.17%   91.18%           
=======================================
  Files          47       47           
  Lines        5462     5465    +3     
=======================================
+ Hits         4980     4983    +3     
  Misses        482      482           

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[machow]

reviewed while pairing...

[machow]

LGTM, thanks!