Changing terminology for adding PostHog to your app

[corywatilo]

Our terminology about installing PostHog is confusing because of the self-hosted aspect. We've traditionally used the following:

• Self hosting: Install, Deploy
• Adding tracking code: Integrating

But people are likely to search/look for "install" because that's traditionally what other platforms call it:

Since we're focusing on Cloud, it would make sense for us to move away from "Integrate" in lieu of "Install", and continue to use "Deploy" for self-hosting.