Code organization, cleanup, linting, packages updates

[Zequez]

• Added a shared folder for stuff used on both Home and GamezPane screens; and accompanying import alias
• Moved files on either Home and GamezPane folders accordingly
• Fixed all TypeScript errors, UI check script runs clean
• Added prettier and improved prettier configuration; added a dependency sorting plugin but it turns out it doesn't support .svelte files yet. However it might soon, and on the prettier configuration it documents how the imports are meant to be sorted: "third-party", "holochain/LrL", "shared", "relative"
• Updated svelte-check to latest version, which resolved a bunch of issues
• Process all UI files through prettier
• Updated CI to work with latest Nix version, and to run TypeScript checks using svelte-check on the UI workspace
• Update to Svelte 4, Typescript 5, Vite 5; and all other deps on /ui
• Use same loader component everywhere
• Removed many unused files