chart.js: add ChartOptions.onHover alias and amend type (#24740)

Present in 2.7 as per docs and code

types/chart.js/chart.js-tests.ts

@@ -21,6 +21,9 @@ const chart: Chart = new Chart(new CanvasRenderingContext2D(), {
         hover: {
             intersect: true
         },
+        onHover(ev: MouseEvent, points: any[]) {
+          return;
+        },
         tooltips: {
             filter: data => Number(data.yLabel) > 0,
             intersect: true,

types/chart.js/index.d.ts

@@ -184,6 +184,7 @@ declare namespace Chart {
         aspectRatio?: number;
         maintainAspectRatio?: boolean;
         events?: string[];
+        onHover?(this: Chart, event: MouseEvent, activeElements: Array<{}>): any;
         onClick?(event?: MouseEvent, activeElements?: Array<{}>): any;
         title?: ChartTitleOptions;
         legend?: ChartLegendOptions;
@@ -291,7 +292,7 @@ declare namespace Chart {
         mode?: string;
         animationDuration?: number;
         intersect?: boolean;
-        onHover?(active: any): void;
+        onHover?(this: Chart, event: MouseEvent, activeElements: Array<{}>): any;
     }
 
     interface ChartAnimationObject {