Add a design system (#34)

* Add theming system

* Add standard Button control and update RadioButtons

* Unify radiobutton with design system

* Update debug screen to have multiple views

* Add ToggleButton

* Update error controls to use design system

* Add typography to <Text> element

* Move DropdownButton into the design system

* Clean out old code

* Move Text into design system

* Add 'inverted' color palette

* Move LoadingPlaceholder into the design system

src/lib/functions.ts

@@ -0,0 +1,6 @@
+export function choose<U, T extends Record<string, U>>(
+  value: keyof T,
+  choices: T,
+): U {
+  return choices[value]
+}