T44d Web · Gallery builds for wasm32: one story per section by URL, themed by the host

The gallery's entry runs natively or, on wasm32, from a wasm_bindgen start
through gpui_web, single-threaded with WebGL2 fallback. ?page, ?story and
?theme choose what shows; an unknown one fails in the page and the log.
set_theme switches the mode later. Pictures load from ELY_GALLERY_ASSETS.
scripts/stories.py writes examples/gallery/stories.json from the pages.

examples/gallery/pages/documents/knowledge.rs

@@ -20,18 +20,9 @@ use crate::{
 };
 
 const COVERS: [&str; 3] = [
-    concat!(
-        env!("CARGO_MANIFEST_DIR"),
-        "/examples/gallery/assets/atrium.jpg"
-    ),
-    concat!(
-        env!("CARGO_MANIFEST_DIR"),
-        "/examples/gallery/assets/dunes.jpg"
-    ),
-    concat!(
-        env!("CARGO_MANIFEST_DIR"),
-        "/examples/gallery/assets/atrium-olive.jpg"
-    ),
+    asset!("atrium.jpg"),
+    asset!("dunes.jpg"),
+    asset!("atrium-olive.jpg"),
 ];
 
 fn favorite(key: &str, icon: &str, title: &str) -> Favorite {