Move to Skeleton for UI Components

[TheLostLambda]

Skeleton should let us use tailwind and give us some nice UI components to quickly mock up a UI that looks pretty nice!

It's already been pulled in as a dependency and set up, so the App.svelte just needs some changing!

[TheLostLambda]

This is now underway!

• [ ] I need to find a way to add nice colours
• [ ] Implement a dialog for adding a tool
• [ ] Implement light / dark mode