Link to antialiasing by code in the 3D Antialiasing page

**Your Godot version:** 4.7.1

**Issue description:**
The documentation for setting anti-aliasing by code is very hard to find. Even if you already know what you're looking for (which is a moot point as you wouldn't be performing a search), the information is split across several pages with no links between them.

Searches typically take you to the 3D antialiasing page, which has no links to the project settings ( https://docs.godotengine.org/en/stable/tutorials/editor/project_settings.html ) for anti-aliasing or viewport settings ( https://docs.godotengine.org/en/stable/classes/class_viewport.html ) for anti-aliasing.

Changing anti-aliasing by code (e.g. when implementing a settings menu) requires gathering information that is split across pages that do not mention each other. The ProjectSetting page doesn't explain the enums used for antialiasing (e.g. I _assume_ they are the same as the ViewPort enums, but the ViewPort uses an enum called VIEWPORTMSAA not PROJECTMSAA or something, so how can I be sure?).

Screen-space anti-aliasing is just as bad. The ProjectSetting documentation provides no insight to the associated enum values, which are recorded in the RenderingServer documentation (for which there is no link from the ProjectSetting page).

I came across this problem while trying to implement a settings menu. Searching the Godot documentation only led me to the 3D Antialiasing page. Web searches also sent me to the same place. Worse - a search engine LLM summary provided a bunch of enums; I wanted to verify this data and had to dig through pages and guess my way to the right place, and then found the LLM information was incorrect - not too surprised, but someone less inclined to go through a dozen docs pages to find the right information might assume the information is simply too obscure.

This made the documentation process feel hostile instead of helpful. This is the kind of frustration that could easily discourage a developer, which is surely the opposite of what we want.

**URL to the documentation page (if already existing):** https://docs.godotengine.org/en/latest/tutorials/3d/3d_antialiasing.html

Start with the 3D Antialiasing page at tutorials/3d/3d_antialiasing.html and review the linked Project Settings and Viewport documentation. Trace the anti-aliasing settings and enum references into the RenderingServer documentation, then add links between the relevant pages so readers can verify the code-facing options and enum values.

Written by the indexing model from the issue text.