test: create test to check for case enablePersistence & synchronizeTabs

when the developer sets:
```
await firestore.enablePersistence({
synchronizeTabs: true
})
```
all chrome tabs sync the local data _via_ the indexedDB local data, so preventing updating the local store on "local updates" completely, means the other tabs will not receive those changes.

I need an automated test that confirms this.......... o_O

perhaps Cypress and a test site will be needed, but only if Cypress can do multiple tabs. (2 Cypress instances would not be the correct tab)

if not possible with Cypress I'm at a loss how to create an automated test for this.