Auto update doesn't work

Currently, there is no auto-update script to call flatpak-node-generator. Otherwise, all other dependencies are updated correctly.

```sh
flatpak-node-generator pnpm SlimeVR-Server/pnpm-lock.yaml
```

I am a bit concerned about [getting node version from master branch](https://github.com/flathub/dev.slimevr.SlimeVR/blob/master/dev.slimevr.SlimeVR.yml#L120), but i think it shouldn't be a problem in most cases — it almost definitely will either fail to build or produce a properly working build.

Start with the existing dependency update workflow and dev.slimevr.SlimeVR.yml, especially the node version reference around line 120. Check how SlimeVR-Server/pnpm-lock.yaml is currently handled and where flatpak-node-generator should be invoked. Done means the auto-update process also regenerates the Flatpak Node dependencies and remains buildable.

Written by the indexing model from the issue text.