Only try to use navigator.share on mobile

src/Game.tsx

@@ -99,22 +99,27 @@ function Game(props: GameProps) {
   };
 
   async function share(url: string, copiedHint: string, text?: string) {
+    if (
+      /android|iphone|ipad|ipod|webos/i.test(navigator.userAgent) &&
+      !/firefox/i.test(navigator.userAgent)
+    ) {
       try {
         await navigator.share({ url, text });
         return;
       } catch (e) {
         console.warn("navigator.share failed:", e);
+      }
+    }
     try {
       const body = url + (text ? "\n\n" + text : "");
       await navigator.clipboard.writeText(body);
       setHint(copiedHint);
       return;
-      } catch (e2) {
+    } catch (e) {
-        console.warn("navigator.clipboard.writeText failed:", e2);
+      console.warn("navigator.clipboard.writeText failed:", e);
+    }
     setHint(url);
   }
-    }
-  }
 
   const onKey = (key: string) => {
     if (gameState !== GameState.Playing) {
@@ -287,8 +292,7 @@ function Game(props: GameProps) {
             }}
           >
             Challenge a friend to this word
-          </button>
+          </button>{" "}
-          {" "}
           <button
             onClick={() => {
               share(