Update ssr-writing-universal-code.md (#617)
Update ssr-writing-universal-code.md (#617)

I was missing this piece of information when I was implementing SSR for my project. Even with the Store exported as a function, if we use modules, the state of each module is considered a singleton if it's not exported as a function as well.
rstoenescu/quasar-site,rstoenescu/quasar-site,quasarframework/quasar-framework.org,rstoenescu/quasar-site,quasarframework/quasar-framework.org,quasarframework/quasar-framework.org