Let users browse followers and following lists

Following lists are public; followers are visible to the user and to mutual followers.
Adds GET /users/{id}/followers and /following, exposes isFollowing and canViewFollowers
on the profile, and returns isFollowedByViewer from user search so the web player no
longer calls /is-following per user.

web-player/src/lib/config.ts

@@ -17,5 +17,6 @@ export const HOME_POPULAR_MAX = 8;
 export const PLAYLIST_PICKER_PAGE_SIZE = 50;
 export const LIKED_TRACKS_PAGE_SIZE = 500;
 export const EXPLORE_USERS_LIMIT = 12;
+export const FOLLOW_LIST_PAGE_SIZE = 30;
 export const MENU_WIDTH = 240;
 export const SUBMENU_WIDTH = 256;