Add Follow Button for Individual Users

[Mephistic]

Problem

As part of our social layer work, we want to give users the ability to "follow" Organizations and other Users so they can be notified when orgs/users they're interested in publish new testimony. We currently have the follow button set up (behind a feature flag) for Organizations, but do not have a corresponding button for regular Users.

We would to add the "Follow" buttons that currently exist for Organizations to regular User content as well.

For now, let's say we'll continue to use the same "followOrg"/"unfollowOrg" firebase functions for users as well (since orgs are just a type of user) - we'll check in with Arun to see how we want to handle this going forward (might make sense to rename the firebase function if we're going to support more kinds of user).

Success Criteria

• "Follow" button added to User Profile Page (identical in design to the one currently on the Organization Profile Page)
• "Follow" button added to Browse Testimonies Page in the search results (identical in design to the button currently displayed by Organization search results on the Browse Testimonies Page)

Additional Links

• Example of the Org Follow Button on the Browse Testimonies Page: https://maple-dev.vercel.app/testimony?publishedTestimony%2Fsort%2FpublishedAt%3Adesc%5BrefinementList%5D%5Bcourt%5D%5B0%5D=193&publishedTestimony%2Fsort%2FpublishedAt%3Adesc%5BrefinementList%5D%5BauthorRole%5D%5B0%5D=organization
• Example of the Org Follow Button on the Org Profile Page: https://maple-dev.vercel.app/profile?id=8P5Ar8NyAcNEVJMTexezXvRbept2

[simk209]

I'm going to hold off on this until Laura does some work on issue 1592 to lower the risk we run into weird issues due to working on it simultaneously.