fix(tooltip): Correct the type of selectedData

Change the type of selectedData as an array of DataItem

Fix #2056
Close #2058

AUTHORS.txt

@@ -45,3 +45,4 @@ Alan Hamlett <[email protected]>
 Nicolas Forêt <[email protected]>
 Marc Faber <[email protected]>
 Donald Pipowitch <[email protected]>
+Sung Oh Park <[email protected]>

types/options.d.ts

@@ -1046,22 +1046,22 @@ export interface TooltipOptions {
 	/**
 	 * Set a callback that will be invoked before the tooltip is shown.
 	 */
-	onshow?(this: Chart, selectedData: DataItem): void;
+	onshow?(this: Chart, selectedData: DataItem[]): void;
 
 	/**
 	 * Set a callback that will be invoked after the tooltip is shown
 	 */
-	onshown?(this: Chart, selectedData: DataItem): void;
+	onshown?(this: Chart, selectedData: DataItem[]): void;
 
 	/**
 	 * Set a callback that will be invoked before the tooltip is hidden.
 	 */
-	onhide?(this: Chart, selectedData: DataItem): void;
+	onhide?(this: Chart, selectedData: DataItem[]): void;
 
 	/**
 	 * Set a callback that will be invoked after the tooltip is hidden.
 	 */
-	onhidden?(this: Chart, selectedData: DataItem): void;
+	onhidden?(this: Chart, selectedData: DataItem[]): void;
 
 	/**
 	 * Set if tooltips on all visible charts with like x points are shown together when one is shown.