Update vuex-store.md (#8406)
Update vuex-store.md (#8406)

* Update vuex-store.md

Clarification for Dummies like me. Explains how to add vuex to an existing project.

* Update vuex-store.md

Co-authored-by: Paolo Caleffi <ca6a7f5545343c58065f3a9653d608fe8e65eb95@dreamonkey.com>
quasarframework/quasar,quasarframework/quasar,quasarframework/quasar,rstoenescu/quasar-framework,quasarframework/quasar,rstoenescu/quasar-framework,rstoenescu/quasar-framework