feat(container.scss): add container styles for fixed position and scrolling behavior

feat(container.ts): create container module to handle scrollable behavior and add/remove disableScroll class

fix(customCursor.ts): update append target for cursor element to use container instead of main

fix(stage.ts): update append target for stage element to use container instead of main

fix(stageNav.ts): update append target for navOverlay element to use container instead of main

feat(main.ts): initialize container module and conditionally initialize stage and stageNav modules based on device type

fix(nav.ts): update references to state module functions to use state.get() instead of getState()

assets/ts/nav.ts

@@ -1,4 +1,4 @@
-import { getState, incThreshold, decThreshold } from './state'
+import { decThreshold, incThreshold, state } from './state'
 import { expand } from './utils'
 
 /**
@@ -48,15 +48,15 @@ export function initNav() {
 // helper
 
 export function updateThresholdText(): void {
-  const thresholdValue: string = expand(getState().threshold)
+  const thresholdValue: string = expand(state.get().threshold)
   thresholdDispNums.forEach((e: HTMLSpanElement, i: number) => {
     e.innerText = thresholdValue[i]
   })
 }
 
 export function updateIndexText(): void {
-  const indexValue: string = expand(getState().index + 1)
-  const indexLength: string = expand(getState().length)
+  const indexValue: string = expand(state.get().index + 1)
+  const indexLength: string = expand(state.get().length)
   indexDispNums.forEach((e: HTMLSpanElement, i: number) => {
     if (i < 4) {
       e.innerText = indexValue[i]