feat(UI): Enhancement to the admin dashboard page issue - search bar

The admin page currently displays ALL users in the prisma database. We believe the prisma database will be very large when the Classroom app is deployed, so a search feature to look for a user by name, email, or role would be a helpful addition.

**Original admin table:**

Steps to recreate the issue:

1. Make sure you can successfully log in via Github (use the Github sign-in option, not Auth0)
2. Run "npx prisma studio" in the terminal, navigate to the "Users" table, change the role of your user to "ADMIN"
3. Make sure you click "Save changes" in prisma studio
4. Sign out of the Classroom app and then sign back in
5. Navigate to the /admin page (type this into the browser)