Large canvas not downsized properly when running wasm build in mobile on itch.io

I'm having trouble with the canvas overflowing when using this template targeting mobile devices and publishing on itch.io.

I'm quite sure the change in this PR https://github.com/bevyengine/bevy_github_ci_template/pull/44 previously fixed the issue and properly resized the canvas to fit smaller screens, by adding the css

```

html, body {margin:0;height:100%;}

```

and configuring the window plugin to use `fit_canvas_to_parent: true`.

But something has changed 🤔 and this does not seem to help anymore as a canvas/window with dimensions larger then the target device will overflow and only show a cropped center part of the canvas/window content, when running on mobile on itch.io.

Anyone having the same issue (with itch.io in particular) and have found a workaround / fix?

まず、itch.io を通じて公開されている WASM ビルドをモバイルデバイスで再現し、次にその canvas の動作を PR 44 の設定と比較します。最初に、表示されている CSS と window plugin の設定を確認してください。canvas がオーバーフローやコンテンツの切り取りなしで対象デバイスに収まれば完了です。

索引モデルが issue の本文から書いたものです。