feat(picker): add the speedrun mood and the speedrun.com link

"What to play next" gets a Speedrun mood. The game detail links the
game's speedrun.com page when Core found one with verified runs; only
https://www.speedrun.com/ links are shown.

public/i18n/en.json

@@ -185,6 +185,7 @@
     "NOT_FOUND": "Game not in your library.",
     "PLAYTIME": "Playtime: {{time}}",
     "OPEN_IN_STEAM": "View on Steam",
+    "OPEN_IN_SPEEDRUN": "Speedruns on speedrun.com",
     "ACHIEVEMENTS": "Achievements",
     "UNLOCKED": "Unlocked",
     "REMAINING": "Remaining",
@@ -312,10 +313,13 @@
       "COOP": "Co-op",
       "CHILL": "Chill",
       "ACTION": "Action",
-      "SCARY": "Scary"
+      "SCARY": "Scary",
+      "SPEEDRUN": "Speedrun"
     },
     "MOOD_HINT": "Only games whose genre IGDB knows.",
-    "EMPTY_MOOD": "No backlog game fits. Try another mood or length. New games get their mood a moment after the first pick."
+    "MOOD_HINT_SPEEDRUN": "Only games with verified runs on speedrun.com. The backlog is checked in the background, about one game every few seconds.",
+    "EMPTY_MOOD": "No backlog game fits. Try another mood or length. New games get their mood a moment after the first pick.",
+    "EMPTY_SPEEDRUN": "No backlog game with speedruns found. New games may still be checked in the background; try again in a few minutes."
   },
   "MANUAL_GAME": {
     "ADD_BUTTON": "Add game",