Add shadows plugin

[tomas7770]

Description

Adds the base interface plugin for shadows, which registers shadow caster components.

Checklist

• [x] Self-review changes.
• [ ] Evaluate impact on the documentation.
• [ ] Ensure test coverage.
• [ ] Write new samples.
• [x] Add entry to the changelog's unreleased section.

[github-actions[bot]]

PR Preview Action v1.4.7 :---: :rocket: Deployed preview to https://GameDevTecnico.github.io/cubos/docs-preview/pr-1271/ on branch gh-pages at 2024-06-26 15:05 UTC

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 0% with 24 lines in your changes missing coverage. Please review.

Project coverage is 40.58%. Comparing base (e92064d) to head (7afdf8b).

Files	Patch %	Lines
engine/src/render/shadows/directional_caster.cpp	0.00%	7 Missing :warning:
engine/src/render/shadows/caster.cpp	0.00%	5 Missing :warning:
engine/src/render/shadows/plugin.cpp	0.00%	4 Missing :warning:
engine/src/render/shadows/point_caster.cpp	0.00%	4 Missing :warning:
engine/src/render/shadows/spot_caster.cpp	0.00%	4 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #1271 +/- ## ========================================== - Coverage 40.61% 40.58% -0.04% ========================================== Files 354 359 +5 Lines 26330 26354 +24 ========================================== Hits 10695 10695 - Misses 15635 15659 +24 ```

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