Allow embedders to customize link decorations independently

See microsoft/vscode#95631

src/browser/Types.d.ts

@@ -172,12 +172,17 @@ interface ILinkProvider {
 interface ILink {
   range: IBufferRange;
   text: string;
-  hideDecorations?: boolean;
+  decorations?: ILinkDecorations;
   activate(event: MouseEvent, text: string): void;
   hover?(event: MouseEvent, text: string): void;
   leave?(event: MouseEvent, text: string): void;
 }
 
+interface ILinkDecorations {
+  pointerCursor: boolean;
+  underline: boolean;
+}
+
 interface IBufferRange {
   start: IBufferCellPosition;
   end: IBufferCellPosition;