Support basic adding to playlists (#157)

Closes #143 

Adds option in the "More" menu to add the item to a playlist. Can also
create a playlist if needed.

app/src/main/java/com/github/damontecres/wholphin/util/TransformList.kt

@@ -0,0 +1,11 @@
+package com.github.damontecres.wholphin.util
+
+class TransformList<S, T>(
+    private val source: List<S>,
+    private val transform: (S) -> T,
+) : AbstractList<T>() {
+    override val size: Int
+        get() = source.size
+
+    override fun get(index: Int): T = transform.invoke(source[index])
+}