Add PHP8.3 to automated test suite

[jakejackson1]

Description

Include PHP 8.3 when running PHPUnit

Testing instructions

Let GitHub Actions do its thing

Screenshots

Checklist:

• [ ] I've tested the code.
• [ ] My code is easy to read, follow, and understand
• [ ] My code follows the accessibility standards.
• [ ] My code has proper inline documentation / docblocks.

Additional Comments

[codecov[bot]]

Codecov Report

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

Comparison is base (c56e361) 75.13% compared to head (fa5cd75) 72.81%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## development #1483 +/- ## ================================================= - Coverage 75.13% 72.81% -2.33% Complexity 2951 2951 ================================================= Files 243 186 -57 Lines 12880 11416 -1464 Branches 370 0 -370 ================================================= - Hits 9678 8312 -1366 + Misses 3194 3104 -90 + Partials 8 0 -8 ```

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