Create posthog dashboards and add more tracking

[jagodarybacka]

### Tasks
- [ ] https://github.com/tahowallet/dapp/issues/696
- [x] Create chart - average time spent on the dapp
- [x] Create chart - average number of users at any given time
- [x] Create chart - realms opened (by date, by realm id)
- [x] Create chart - visitors device (desktop or mobile)

[Shadowfiend]

Pageleave is going to be very hard/maybe impossible due to browser limitations, fwiw.

Thinking some more here, we might be able to do a little bit more in PostHog by measuring anything that has >15 minutes (or whatever) between actions as a new “session” for our purposes. We can fiddle with the constant a bit.

Note that realm opens already have a chart, but we don't have the realm id with them right now.

[jagodarybacka]

I was thinking we can use before unload event 🤔

realm opens already have a chart, but we don't have the realm id

I think it was fixed a couple days ago? Will check

[ioay]

I've just added the following charts to Posthog: https://app.posthog.com/insights?createdBy=61067. @Shadowfiend could you confirm if it is enough, do we need an additional dashboard for this analytics?

[jagodarybacka]

• Unique users device type - would be good to add labels to the data so we know from looking at the chart what color refers to what device
• Realms opened by realm name - looks good
• Number of unique users - looks good I think
• Average time spent on the dapp - seems highly improbable that the average time is larger than a few minutes, are we calculating that correctly?