[DOCS] Flesh out Engine Developer Guide

[ShaunaGordon]

Describe the issue briefly

https://docs.o3de.org/docs/engine-dev/ is largely only stubs, which some sections not even having valid links. This entire section really needs some love. We can use this issue to help enumerate the specifics.

Which page(s) / section(s) are affected?

https://docs.o3de.org/docs/engine-dev/

Does this work have an engineering dependency? What is it?

There are probably some, technically, since this section is so expansive and there's always work going on on the engine, but I think that's not really an issue while we lay more of the foundation.

[tkothadev]

For the engine developer guide, do we have a mechanism for anchoring documentation to a release version of o3de? Trying to keep the guide up to date with the developer branch in my opinion would be a fruitless endeavor, as too much activity happens there.

Release cycle is slow enough that you could get enough meaningful documentation out, especially for things like AZFramework and Core, which are unlikely to change

[ShaunaGordon]

We can, yeah. You can see that we're currently working on the 24.09 engine version (to release soon), and are cutting a version of the docs to correspond with it.

The way we work is that updates go to development by default, and while it's roughly in sync with the development version of the engine, "development" here also reflects the latest version of the docs themselves. We then cut branches that correspond to the versions of the engine, using the same process the engine repo uses, to "freeze" a copy of the docs to that version (it's not a hard freeze, since we can and do cherry-pick back as necessary).

I think, too, once we get a good foundation, keeping the development docs branch more in sync with the development engine branch will get easier, since then we're dealing more in changes, and less in wholesale synthesis.

[ShaunaGordon]

I've created a Github project for this to help with enumerating the pages we need - https://github.com/orgs/o3de/projects/63/views/1 (projects are only visible to org members unfortunately, but it's better than nothing)