feat(follow): add feed links, following page and tile (#52, #51)

Feed links go to the game and to the profile view of that game.
Add /following page, nav item and an opt-in Following tile.
Games not in your library show a catalog view with an add button.

README.md

@@ -21,7 +21,7 @@ To Be Played is split into four repositories:
 ## Features
 
 - **Dashboard** with an edit mode ("Customize"): the user orders, hides and resizes the tiles (small = half width
-  and less content, large = double width and more), and can add the stat groups of "Your stats" as tiles. Stored
+  and less content, large = double width and more), and can add the stat groups of "Your stats" and a "Following" tile. Stored
   in Auth, so it follows the user to the phone; "Reset" goes back to the default. Tiles: most played games and games in progress (one call, `GET /api/library/dashboard-games`), "Pile of Shame" with backlog hours, its trend of the last 90
   days ("this month: +N added, -N off the pile") and a random suggestion,
   Steam avatar and a banner from the most played game of the last two weeks, and an achievement card: unlocked
@@ -185,6 +185,14 @@ flowchart LR
   who goes private ends the follow with a note. Two more notes come from the user's own
   PlayStation link (`PSN_EXPIRING` about 2 days before it ends, `PSN_EXPIRED` when it has ended), with a link to the
   settings. Notes older than 90 days are deleted.
+  The feed links on (#52): the person's name goes to their profile while it is public (`profileName`), a game goes to
+  your own game page (`/library/<appid>`), and "on their profile" opens `/u/<name>?game=<appid>`, which shows that
+  game above the tiles (`ProfileGameCard`: status, playtime, achievements, only what the profile shares; one message
+  when it hides or does not have the game). A game you do not own opens a catalog view (`CatalogGameCard`, `GET
+  /api/library/games/<appid>/preview`) with an "Add to my library" button that opens the add search with the name filled
+  in. `/following` (nav item "Following", #51) lists the people you follow, newest feed message first, with an initial
+  letter instead of an avatar, and "Unfollow"; the "Following" dashboard tile (opt-in via "Customize") shows the first
+  3, 5 or 10 of them and loads its own data.
 - **What's new**: a dialog on the dashboard shows the news entries the user has not seen yet, newest first. "Got it"
   marks them seen in Auth; closing the dialog any other way shows them again on the next dashboard visit. `/whats-new`
   (menu) lists all entries and marks them seen. Admins publish, preview, edit and delete entries on `/admin/news`.