fix Format url

Author: AndreiKingsley

core/src/main/kotlin/org/jetbrains/kotlinx/dataframe/documentation/DocumentationUrls.kt

@@ -131,4 +131,7 @@ internal interface DocumentationUrls {
 
     /** [See `Data Schemas/Data Classes Generation` on the documentation website.]({@include [Url]}/dataschemagenerationmethods.html) */
     interface DataSchemaGeneration
+
+    /** [See `format` on the documentation website.]({@include [Url]}/format.html) */
+    interface Format
 }