Add option to not crop image previews (#2832)

* Don't crop image previews with aspects between 2:1 & 1:2

Fixes #1995

* Custom media preview layout for handling various aspect ratios

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

@@ -68,7 +68,9 @@ data class Attachment(
     @Parcelize
     data class MetaData(
         val focus: Focus?,
-        val duration: Float?
+        val duration: Float?,
+        val original: Size?,
+        val small: Size?,
     ) : Parcelable
 
     /**
@@ -82,4 +84,14 @@ data class Attachment(
         val x: Float,
         val y: Float
     ) : Parcelable
+
+    /**
+     * The size of an image, used to specify the width/height.
+     */
+    @Parcelize
+    data class Size(
+        val width: Int,
+        val height: Int,
+        val aspect: Double
+    ) : Parcelable
 }