Support sessionStorage for persistence_type

[odaysa]

Hello,

I see that Mixpanel supports localStorage and Cookie for persistence_type.
As known, localStorage and Cookies are shared between tabs, which can effect the expected behavior of the application, one tab can change the super properties of the other tab.
Supporting sessionStorage will enable the independency of the super properties keeping them encapsulated for that tab.
The shared resource between the tabs caused serious issues in our application that I had to solve by created my own super properties...

[tdumitrescu]

Interesting. For most applications, it's desirable to share super properties across tabs. But sessionStorage and localStorage are API-compatible, so it shouldn't be too much work to offer it as a persistence option for those who need it.

[odaysa]

I found another issue in our system because of this...
"time_event" also stored in the cookies, different tabs with same event name will have wrong duration values...
How can we sort this issues quickly?