Add three-up evidence boards for El Capitan and Joke Shop

docs/screens/boards/elcapitan-day-board.json

@@ -0,0 +1,7 @@
+{
+  "board": "elcapitan-day-board.jpg",
+  "caption": "El Capitan facade, day: 2009 CC BY photo | photo-anchored concept | current capture",
+  "photo": "docs/screens/refs/hollywood/el-capitan-facade-day-wikimedia-2009-10-27.jpg",
+  "concept": "docs/screens/concepts/hollywood_boulevard/hollywood_boulevard_entrance_day-v2.png",
+  "capture": "docs/screenshots/01-venue-overview.png"
+}