Create a new admin navbar option that is shown only for users that are MASTER users.
[x] It should have a list of users but only show the 20 users that last signed up.
[x] Allow searching for a user by email and name. Add a search button so this way the database will only be accessed once the master user is done typing (to prevent countless reads that may happen, especially after the app gets to tens of thousands of users).
[x] Add the ability to change a regular user to an admin user and vice-versa.
Create a new admin navbar option that is shown only for users that are MASTER users.