Open photos embedded in preview cards in the image viewer (#1966)

* Open photos embedded in preview cards in the internal image viewer instead of opening the browser

* Enable toolbar for single image viewer

* Apply review feedback

app/src/main/java/com/keylesspalace/tusky/entity/Card.kt

@@ -27,7 +27,8 @@ data class Card(
         val type: String,
         val width: Int,
         val height: Int,
-        val blurhash: String?
+        val blurhash: String?,
+        val embed_url: String?
 ) {
 
     override fun hashCode(): Int {
@@ -42,4 +43,7 @@ data class Card(
         return account?.url == this.url
     }
 
+    companion object {
+        const val TYPE_PHOTO = "photo"
+    }
 }