Use Mardown code block for hover tooltip

src/languageFeatures.ts

@@ -330,7 +330,7 @@ export class QuickInfoAdapter extends Adapter implements monaco.languages.HoverP
 			return {
 				range: this._textSpanToRange(resource, info.textSpan),
 				contents: [{
-					value: contents
+					value: '```js\n' + contents + '\n```\n'
 				}, {
 					value: documentation + (tags ? '\n\n' + tags : '')
 				}]