Update cross-platform targeting

[FantasticFiasco]

Description

Remove support for .NET Standard 1.3, aligning with the cross-platform targeting library guidance.

Checklist

• [x] My code follows the style guidelines of this project
• [x] I have performed a self-review of my own code
• [x] I have commented my code, particularly in hard-to-understand areas

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 90.47%. Comparing base (1138907) to head (3e857c2).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #197 +/- ## ======================================= Coverage 90.47% 90.47% ======================================= Files 10 10 Lines 252 252 Branches 42 42 ======================================= Hits 228 228 Misses 12 12 Partials 12 12 ```

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