Support computed properties from a static enum-like object

[Silverwolf90]

Here's the corresponding issue in xstate-parser: statelyai/xstate-parser#8

Currently, any guards/actions used in these nested objects are being flagged as not used in the machine by the extension.

Repro: https://codesandbox.io/s/zen-frog-d750i?file=/src/index.ts