add kdoc for pagination

core/src/main/kotlin/com/insanusmokrassar/postssystem/core/utils/pagination/Pagination.kt

@@ -1,6 +1,20 @@
 package com.insanusmokrassar.postssystem.core.utils.pagination
 
+/**
+ * Base interface of pagination
+ *
+ * If you want to request something, you should use [SimplePagination]. If you need to return some result including
+ * pagination - [PaginationResult]
+ */
 interface Pagination {
+    /**
+     * Started with 0.
+     * Number of page inside of pagination. Offset can be calculated as [page] * [size]
+     */
     val page: Int
+    /**
+     * Can be 0, but can't be < 0
+     * Size of current page. Offset can be calculated as [page] * [size]
+     */
     val size: Int
 }