Allow scroll bar interaction in demo in screenReaderMode

Fixes #2757

css/xterm.css

@@ -146,7 +146,6 @@
     left: 0;
     top: 0;
     bottom: 0;
-    right: 0;
     z-index: 10;
     color: transparent;
 }

src/browser/AccessibilityManager.ts

@@ -277,6 +277,7 @@ export class AccessibilityManager extends Disposable {
     if (!this._renderService.dimensions.css.cell.height) {
       return;
     }
+    this._accessibilityTreeRoot.style.width = `${this._renderService.dimensions.css.canvas.width}px`;
     if (this._rowElements.length !== this._terminal.rows) {
       this._handleResize(this._terminal.rows);
     }