Record a video of the install process on all platforms

To graphically show how to use the installer, I think a video is the most effective way, rather than our current list of instructions. Having a recording for each platform would also be useful for explaining on Linux/MacOS as most of us are not familiar with those platforms/don't have a PC on those platforms.

This is also useful when debugging, since users can say "this part at 1:00 in the video doesn't happen", rather just explain that "nothing happens".

I actually recorded a video already just for the "partial manual install" because that is difficult to explain otherwise: https://www.youtube.com/watch?v=Px4JWsSycQE (this video is linked inside the installer)

I wouldn't be too worried about needing to update the video if something changes, since the basic install process hasn't changed in a very long time.

- [ ] Windows Video
- [ ] MacOS Video
- [ ] Linux Video
- [ ] Steam Deck Video
- [ ] This is a big pain point, because many Steam Deck users have a Windows background and are unfamiliar with using the Konsole + Steam Deck's desktop mode + proton/native etc. A video going through what we already have on the wiki would be very useful.
- [ ] This could be done without a steam deck by installing SteamOS on a PC, see [steampowered.com - Build your own Steam Machine](https://store.steampowered.com/steamos/buildyourown)

この issue は、Windows、macOS、Linux、Steam Deck でのインストールプロセスの動画記録を求めています。まず、既存の wiki の手順とリンクされている部分的な手動インストールの動画を確認してください。画面録画ソフトウェアを使用して手順をキャプチャし、現在のインストーラーのワークフローに従うようにしてください。動画は YouTube などのプラットフォームにアップロードし、プロジェクトのドキュメントにリンクする必要があります。

索引モデルが issue の本文から書いたものです。