Revert "Remove accesskit feature and always depend on accesskit (#7701)"

This reverts commit 1af5d1d37e.

crates/eframe/Cargo.toml

@@ -36,7 +36,7 @@ default = [
 ]
 
 ## Enable platform accessibility API implementations through [AccessKit](https://accesskit.dev/).
-accesskit = ["egui-winit/accesskit"]
+accesskit = ["egui/accesskit", "egui-winit/accesskit"]
 
 # Allow crates to choose an android-activity backend via Winit
 # - It's important that most applications should not have to depend on android-activity directly, and can

crates/eframe/src/web/app_runner.rs

@@ -358,7 +358,8 @@ impl AppRunner {
             events: _,                    // already handled
             mutable_text_under_cursor: _, // TODO(#4569): https://github.com/emilk/egui/issues/4569
             ime,
-            accesskit_update: _,        // not currently implemented
+            #[cfg(feature = "accesskit")]
+                accesskit_update: _, // not currently implemented
             num_completed_passes: _,    // handled by `Context::run`
             request_discard_reasons: _, // handled by `Context::run`
         } = platform_output;