add several things into pagination functionality

postssystem.core/src/commonMain/kotlin/com/insanusmokrassar/postssystem/core/utils/pagination/SimplePagination.kt

@@ -2,6 +2,16 @@ package com.insanusmokrassar.postssystem.core.utils.pagination
 
 import kotlinx.serialization.Serializable
 
+const val defaultSmallPageSize = 2
+const val defaultMediumPageSize = 5
+const val defaultLargePageSize = 10
+const val defaultExtraLargePageSize = 15
+
+inline fun FirstPagePagination(size: Int = defaultMediumPageSize) = SimplePagination(
+    page = 0,
+    size = defaultMediumPageSize
+)
+
 @Serializable
 data class SimplePagination(
     override val page: Int,