[v5] Strongly type state and transition `meta`

[davidkpiano]

You can now strongly type meta on state nodes and transitions via stateMeta and transitionMeta respectively:

import { createMachine } from 'xstate';

const machine = createMachine({
  types: {
    stateMeta: {} as { title: string },
    transitionMeta: {} as { button: 'primary' | 'secondary' }
  },
  initial: 'idle',
  states: {
    idle: {
      // Strongly typed from `stateMeta`
      meta: { title: 'Idle' },
      on: {
        CLICK: {
          target: 'loading',
          // Strongly typed from `transitionMeta`
          meta: { button: 'primary' }
        }
      }
    }
  }
});

Fixes https://github.com/statelyai/xstate/issues/809

---

Motivation: strongly-typing things like this: https://github.com/statelyai/xstate/pull/4239/files#diff-a43cf6af3000f32addb10c6176a04f8a5066bc04358b4805726165c65d8565d3R64

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Latest commit: e2f2f142e1d0f1df9be0b5516bb327747b509b33

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[Andarist]

superseded by https://github.com/statelyai/xstate/pull/4863