Refactor app in to its own slice

slices/main/templates/photos/index.html.slim

@@ -0,0 +1,10 @@
+- context.content_for(:title, "Photos | ")
+
+div class="mb-12 prose dark:prose-invert max-w-prose mx-auto text-gray-800 dark:text-gray-200"
+  h1 Photos
+
+div class="grid grid-cols-3 gap-4 mb-4 max-w-prose mx-auto"
+  - photos.each do |post|
+    == render "shared/photo_post", post: post, extended: true
+
+div class="max-w-screen-md mx-auto border-t border-solid border-gray-200 dark:border-gray-600"