use padding-left of 20px for preview part, fixes #5883

src/vs/workbench/parts/html/browser/htmlPreviewPart.ts

@@ -74,6 +74,7 @@ export class HtmlPreviewPart extends BaseEditor {
 
 	public createEditor(parent: Builder): void {
 		this._container = document.createElement('div');
+		this._container.style.paddingLeft = '20px';
 		parent.getHTMLElement().appendChild(this._container);
 	}