Enhance the subscribe api

[ArrayZoneYour]

I have a:

3. [x] Idea:

   • [x] What problem would it solve for you? 🐛 Developer can subscribe the state changes. v2.x api

     // subscribe actions
     // (storeName, actionList, callback) => void
     subscribe('Counter', ['increment'], () => (count += 1))
     // subscribe properties changes
     // (storeName, mapStateFunction, callback) => void
     subscribe('Counter', state => state.count, () => alert('counter count change!'))

     v3.x api

     const store = Store({
       // ...
      actions: {
        updateA: (s, payload) => { ... },
        updateC: (s, payload) => { ... },
        updateD: (s, payload) => { ... }
      }
     })
     // subscribe actions
     store.subscribe(['updateA'], () => (count += 1))
     // subscribe properties changes
     store.subscribe(state => state.A, () => alert('A change!'))

   • [x] Do you think others will benefit from this change as well and it should in core package? 💡 Yes

   • [x] Are you willing to (attempt) a PR yourself? ⚔ Yes