rename app folder to editor (#1528)

Turns out there was one last terrible renaming PR to make. This PR
renames the `@tldraw.editor`'s `app` folder to `editor`. It should not
effect exports but it will be a gnarly diff.

### Change Type

- [x] `internal` — Any other changes that don't affect the published
package (will not publish a new version)

packages/editor/src/lib/hooks/useDocumentEvents.ts

@@ -1,6 +1,6 @@
 import { useEffect } from 'react'
 import { useValue } from 'signia-react'
-import { TLKeyboardEventInfo, TLPointerEventInfo } from '../app/types/event-types'
+import { TLKeyboardEventInfo, TLPointerEventInfo } from '../editor/types/event-types'
 import { preventDefault } from '../utils/dom'
 import { useContainer } from './useContainer'
 import { useEditor } from './useEditor'