Fix to index.md

[grazilenehan]

Proposed changes

Some links were 404s so I've updated them to the following upon request from the Partner:

iOS section
…follow the instructions: https://docs.taplytics.com/docs/guides-push-notifications
…this section of their docs!: https://support.taplytics.com/hc/en-us/articles/360004176632-Deep-Linking-Guide-
For more information about setting up Taplytics on iOS, see their docs: https://docs.taplytics.com/docs/ios-getting-started

Android Section
This document explains how to set up Push Notifications: https://docs.taplytics.com/docs/guides-push-notifications
…this one explains how to set up deep linking: https://support.taplytics.com/hc/en-us/articles/360004176632-Deep-Linking-Guide-

Identify Section
user attributes on Taplytics: https://docs.taplytics.com/docs/guides-user-insights

Merge timing