Add hover and leave callbacks for linkprovider

Fixes #3056.

typings/xterm.d.ts

@@ -352,6 +352,23 @@ declare module 'xterm' {
     willLinkActivate?: (event: MouseEvent, uri: string) => boolean;
   }
 
+  /**
+   * An object containing options for a link provider.
+   */
+  export interface ILinkProviderOptions {
+    /**
+     * A callback that fires when the mouse hovers over a link for a period of
+     * time (defined by {@link ITerminalOptions.linkTooltipHoverDuration}).
+     */
+    hover?(event: MouseEvent, text: string, location: IViewportRange): void;
+
+    /**
+     * A callback that fires when the mouse leaves a link. Note that this can
+     * happen even when tooltipCallback hasn't fired for the link yet.
+     */
+    leave?(event: MouseEvent, text: string): void;
+  }
+
   /**
    * An object that can be disposed via a dispose function.
    */