Descriptive Wiki entries for CMake options

[M2-TE]

The CMake options are currently being described in the README-cmake.md, which seems to be missing some options that may be of interest to people who use CMake's FetchContent or would otherwise build SDL themselves in general.

Examples include stuff like SDL_VULKAN or SDL_OPENGL, support for which is automatically enabled under e.g. Windows. Disabling these manually should not be an issue if the application does not plan on using these graphics APIs (as far as I am aware) and would cut down on compilation time + file size.

Another example would be SDL_PRESEED, of which I'm curious about how it works exactly, as configuration time can be rather long.

It would also be nice if all the CMake configuration options could be put onto the SDL3/FrontPage Wiki, so that these are available at a glance. Currently there's just the SDL3/Installation section, but it focuses more on the different platforms, rather than CMake options themselves, so it might warrant an extra page such as SDL3/CMake.

[slouken]

Feel free to contribute a PR!