Vue initialization and FloatingMenu codebase refactoring and cleanup (#649)

* Clean up Vue initialization-related code

* Rename folder: dispatcher -> interop

* Rename folder: state -> providers

* Comments and clarification

* Rename JS dispatcher to subscription router

* Assorted cleanup and renaming

* Rename: js-messages.ts -> messages.ts

* Comments

* Remove unused Vue component injects

* Clean up coming soon and add warning about freezing the app

* Further cleanup

* Dangerous changes

* Simplify App.vue code

* Move more disparate init code from components into managers

* Rename folder: providers -> state-providers

* Other

* Move Document panel options bar separator to backend

* Add destructors to managers to fix HMR

* Comments and code style

* Rename variable: font -> font_file_url

* Fix async font loading; refactor janky floating menu openness and min-width measurement; fix Vetur errors

* Fix misaligned canvas in viewport until panning on page (re)load

* Add Vue bidirectional props documentation

* More folder renaming for better terminology; add some documentation

frontend/src/utility-functions/math.ts

@@ -0,0 +1,3 @@
+export function clamp(value: number, min = 0, max = 1): number {
+	return Math.max(min, Math.min(value, max));
+}