gh-95451: Update docs for wasm32-emscripten and -wasi platforms (GH-95452)

Co-authored-by: Éric <merwok@netwok.org>
Co-authored-by: Michael Droettboom <mdboom@gmail.com>
Co-authored-by: Ezio Melotti <ezio.melotti@gmail.com>
Co-authored-by: CAM Gerlach <CAM.Gerlach@Gerlach.CAM>
(cherry picked from commit e3b6ff19)

Co-authored-by: Christian Heimes <christian@python.org>