feat: prep for global shell [DHIS2-15635]

[KaiVandivier]

Part of DHIS2-15635

WIP -- more features coming

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• Builds a "pluginified app" to an app.html entry point that can be hosted by a global shell
• Hosts a dev server for the pluginified app
• Use absolute URLs for app runtime to allow client-side routing without breaking the data service
• Build a version of the app to index.html that includes the global shell that hosts the pluginified app.html entrypoint
• Improve the dev experience: currently it's a slow start time that creates a minified production build that runs on a second port, and React Dev Tools aren't available in iframes by default
  • Inject a script import to enable standalone React Dev Tools in the dev build... there might be a way to do this in the plugin Webpack config
  • Using Vite could solve the dev build and server problems
  • If Vite isn't used, fixing the dev build with Webpack is important
• Rework plugin HTML to allow height: 100% plugins
• Remove the headerbar in most cases -- that should live in the Global Shell usually
• Maybe hoist a few features like online status, locale, and server info from Adapter into the Global Shell
• Add the Global Shell to this repo? 🤔