Migrated Bookmark from Java to Kotlin (commons-app#5960)

* Rename Bookmark Pages from `.java` to `.kt`

* Migrated Bookmark Pages to kotlin

Author: neeldoshii

app/src/main/java/fr/free/nrw/commons/bookmarks/BookmarkPages.java

@@ -0,0 +1,8 @@
+package fr.free.nrw.commons.bookmarks
+
+import androidx.fragment.app.Fragment
+
+data class BookmarkPages (
+    val page: Fragment? = null,
+    val title: String? = null
+)