Give it a container and a page of its own

A Dockerfile that builds the bundle and serves it from nginx, matching the
three games already on the site, and the metadata a page needs when it is
somewhere rather than on a laptop: canonical, Open Graph, the two JSON-LD
blocks, and a noscript that describes the game rather than showing an empty
div to anybody who does not run scripts.

No dev proxy, unlike its siblings. They post scores to a shared service and
this one has nothing to post: a game of Diplomacy is not a number, and a
leaderboard reading "reached eleven centres" would be a worse thing to know
about somebody than nothing at all.

The favicon is seven powers round a board in the seven colours the map uses,
with the one supply centre in the middle they are all looking at -- drawn
here rather than drafted in a tool, like every other mark in this
repository.

And a way back out, absolute rather than "/": this is served from a
subdirectory in production and from the root in development, so the relative
answer is right in one of those and points at the game itself in the other.

src/App.css

@@ -471,6 +471,7 @@ header select {
   color: #8c98ab;
 }
 .landing footer p { margin: 0 0 8px; }
+.landing footer .ways { font-size: 0.95rem; color: #cbd6e6; margin-bottom: 12px; }
 
 /* ----------------------------------------------------------- giving up */
 

src/components/Landing.tsx

@@ -105,6 +105,18 @@ export function Landing({
       </div>
 
       <footer>
+        <p className="ways">
+          {/*
+            Absolute rather than "/", because this game is served from a
+            subdirectory in production and from the root in development -- so
+            the relative answer is right in one of those and points at the game
+            itself in the other. The destination is a particular site, and
+            naming it is the honest way to say so.
+          */}
+          <a href="https://games.jcoffey.dev/">The rest of the games</a>
+          {' · '}
+          <a href="https://github.com/Coffey-Labs/great-powers">Source</a>
+        </p>
         <p>
           Great Powers is free software under the{' '}
           <a href="https://www.gnu.org/licenses/agpl-3.0.html">GNU Affero General Public License,