add docs links

Author: AndreiKingsley

core/src/main/kotlin/org/jetbrains/kotlinx/dataframe/api/add.kt

@@ -150,6 +150,8 @@ public typealias AddExpression<T, R> = Selector<AddDataRow<T>, R>
  * }
  * ```
  *
+ * For more information: {@include [DocumentationUrls.Add]}.
+ *
  * @param name name for a new column.
  * If it is empty, a unique column name will be generated.
  * Otherwise, it should be unique for original [DataFrame].
@@ -193,6 +195,8 @@ public inline fun <reified R, T> DataFrame<T>.add(
  * including [newValue][AddDataRow.newValue] to retrieve already computed values of this column
  * in previous rows.
  *
+ * For more information: {@include [DocumentationUrls.Add]}.
+ *
  * Returns a new [DataFrame] with the new column inserted at the given [path].
  * {@include [org.jetbrains.kotlinx.dataframe.documentation.ColumnPathCreation]}
  *
@@ -351,6 +355,8 @@ public class AddDsl<T>(
  * }
  * ```
  *
+ * For more information: {@include [DocumentationUrls.Add]}.
+ *
  * @param body An [AddDsl] expression used to define new columns and column groups.
  * @return A new [DataFrame] with the added columns.
  */
@@ -391,6 +397,8 @@ public fun <T> DataFrame<T>.add(body: AddDsl<T>.() -> Unit): DataFrame<T> {
  * }
  * ```
  *
+ * For more information: {@include [DocumentationUrls.Add]}.
+ *
  * @param name name for a new column.
  * If it is empty, a unique column name will be generated.
  * Otherwise, it should be unique for original group [DataFrame]s.