Remove adding `useShallowStore` from installation steps

[fasetto]

Adding the useShallowStore hook complicates the installation stage. Developers shouldn't be responsible for this.

We can not include this hook in this package, because we don't know anything about the useStore implementation.
But we can use the shallow equality function from zustand.

• Auto-import shallow function from zustand
• Pass the equality fn. to the useStore
• Update the docs accordingly