updated getting-started doc with more examples (pmndrs#2348)

* updated readme with more examples

* moved example to docs from readme

* formatted code with Prettier

---------

Co-authored-by: Ankit Sagar <ankit.sagar@telnesstech.com>

docs/getting-started/introduction.md

@@ -49,6 +49,7 @@ const useStore = create((set) => ({
   bears: 0,
   increasePopulation: () => set((state) => ({ bears: state.bears + 1 })),
   removeAllBears: () => set({ bears: 0 }),
+  updateBears: (newBears) => set({ bears: newBears }),
 }))
 ```