feat: Support PrettyTables v3

[sethaxen]

Description

Adds support for PrettyTables v3 while temporarily retaining support for PrettyTables v2 until v3 compatibility is more prevalent across the ecosystem. Supersedes #62.

Checklist

• PR follows official PR format
• New or updated tests cover the new feature.
• Code style is correct (formatted using JuliaFormatter with BlueStyle).
• The new feature is listed in the Features section of the changelog if the change is non-breaking or the BREAKING CHANGES section if it is breaking.
• The patch version number been incremented if the change is non-breaking or the minor version number been incremented if the change is breaking.

[codecov]

Codecov Report

❌ Patch coverage is 96.15385% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 97.03%. Comparing base (641e45b) to head (a9c5403).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
src/show_prettytable.jl	96.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #83      +/-   ##
==========================================
+ Coverage   97.00%   97.03%   +0.02%     
==========================================
  Files          16       16              
  Lines         836      843       +7     
==========================================
+ Hits          811      818       +7     
  Misses         25       25              

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