Enhance the subscribe api

[ArrayZoneYour]

I have a:

3. Idea:

   • 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!'))

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

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