Prepend root_path to meta path in HttpWasmAssetReader (#10527)

# Objective

Fixes an issue where Bevy will look for `.meta` files in the root of the
server instead of `imported_assets/Default` on the web.

## Solution

`self.root_path.join` was seemingly forgotten in the `read_meta`
function on `HttpWasmAssetReader`, though it was included in the `read`
function. This PR simply adds the missing function call.

crates/bevy_asset/src/io/wasm.rs

@@ -77,7 +77,7 @@ impl AssetReader for HttpWasmAssetReader {
         path: &'a Path,
     ) -> BoxedFuture<'a, Result<Box<Reader<'a>>, AssetReaderError>> {
         Box::pin(async move {
-            let meta_path = get_meta_path(path);
+            let meta_path = get_meta_path(&self.root_path.join(path));
             Ok(self.fetch_bytes(meta_path).await?)
         })
     }