Add links to the corresponding SDL3 pages in the SDL2 wiki pages

[captain0xff]

From discord:

Can we have a link on the SDL2 wiki pages pointing to the SDL3 ones? Search engines prioritise the SDL2 pages and in some cases the SDL3 one is not even there in the top 5 results. There is a message showing that it is the legacy documentation and a link to the SDL3 front page but not to the relevant SDL3 page. This will make migration a lot easier. I think this can be automated by parsing the migration script or guide.

[icculus]

Okay, this is done. I actually had this written before, so I just uncommented it. :)

So this page doesn't have an SDL3 equivalent, looks like it usually does:

https://wiki.libsdl.org/SDL2/SDL_OpenAudio

This one does, so it has a note at the top:

https://wiki.libsdl.org/SDL2/SDL_OpenAudioDevice

We can make that more pronounced or whatever. Otherwise, this is good to go.

[slouken]

I don't think we need to be quite so verbose, maybe, e.g.

[SDL Wiki](https://wiki.libsdl.org/)
(This is the legacy documentation for SDL2, the previous stable version; [SDL3](https://wiki.libsdl.org/SDL3/) is the current stable version.)

can be:

[SDL2 Wiki](https://wiki.libsdl.org/SDL2)

and

[SDL Wiki](https://wiki.libsdl.org/)
[This page also has an [SDL3](https://wiki.libsdl.org/SDL3/SDL_OpenAudioDevice) equivalent.]
(This is the legacy documentation for SDL2, the previous stable version; [SDL3](https://wiki.libsdl.org/SDL3/) is the current stable version.)

can be:

[SDL2 Wiki](https://wiki.libsdl.org/SDL2)
(See [SDL_OpenAudioDevice](https://wiki.libsdl.org/SDL3/SDL_OpenAudioDevice) for the SDL3 version.)

(where SDL_OpenAudioDevice would be the correct symbol for renamed or replaced functions)

and

[SDL Wiki](https://wiki.libsdl.org/)
(This is the documentation for SDL3, which is the current stable version. [SDL2](https://wiki.libsdl.org/SDL2/) was the previous version!)

can be:

[SDL3 Wiki](https://wiki.libsdl.org/SDL3)

After a few months this will settle down and we don't need to be in everyone's face about it.

[icculus]

[SDL3 Wiki](https://wiki.libsdl.org/SDL3)

I'd rather this just say "SDL Wiki" for SDL3.

[icculus]

Okay, I think we're good now.

[icculus]

Wait, no, I broke something.

[slouken]

Can we follow function renaming? e.g. SDL_FreeSurface will point at SDL_DestroySurface?

[slouken]

Actually, never mind, this is to help people landing on the wrong page for Google results, not assist in code migration.

[slouken]

Looks good!