Now apps can have persistent files available during SDL_main()/SDL_AppInit()
and don't have to mess with Emscripten-specific code to prepare the filesystem
for use.
(cherry picked from commit dcc177faa4)
This still had a bunch of text that wasn't updated for SDL3's ability to deal
with pre-user-interaction pages. Same idea, but changed text that suggested
you have to wait to open the audio device.
You can't have two sections with the same name (so it can generate unique
page anchors), so fix one of these, and tweak another thing that _isn't_ a
header but wikiheader's quick-and-dirty parser thinks is one.
This now mentions the main callbacks as a possible option, and removes the
part about prebuilt libraries. The latter can return when Emscripten packages
SDL3.
Fixes#11080.
The internal function SDL_EGL_LoadLibrary() did not delete and remove a mostly
uninitialized data structure if loading the library first failed. A later try to
use EGL then skipped initialization and assumed it was previously successful
because the data structure now already existed. This led to at least one crash
in the internal function SDL_EGL_ChooseConfig() because a NULL pointer was
dereferenced to make a call to eglBindAPI().
