update zustand example

[Munawwar]

Made SSG and SSR code similar. Comments and variable renames on store.js

Checklist:

Documentation / Examples

• [✓] Make sure the linting passes by running yarn lint

[Munawwar]

@leerob Requesting to merge PR. I wrote the initial example some months ago. This PR is just cleanup + comments.

[Munawwar]

rebased branch

[Munawwar]

^ last force push was just rebasing branch again.

[premier213]

how to add multi-state to this example?
store = store ?? initializeStore(serverInitialState)

a new better solution is this:
const store = useMemo(() => initializeStore(state), [state])