Moved Lua & Shader API Reference from Wiki to Repository

[adriengivry]

Description

GitHub wiki's being fairly limited and not very collaborative, this PR moves the scripting & shader API (Lua & GLSL related documentation) directly to the Overload repository.

This will allow:

• Collaborators to update the API alongside their PRs
• Version the API alongside the engine (e.g. Overload 1.8 might have a different Lua API than 1.9)

Note

Tutorials will remain in the Wiki for now, as they are typically image-heavy, which we want to keep out of the repository.

To-Do

• Update engine "Help" menu in the menu bar to point to the repository's API/ folder (based on tag of the current version)
• Update Wiki to have a "Depreciation notice" for its scripting API

Related Issue(s)

Fixes #(issue number)

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Checklist

• My code follows the project's code style guidelines
• I have commented my code, particularly in hard-to-understand areas
• I have updated the documentation accordingly
• My changes don't generate new warnings or errors