Enable math in markdown preview

Fixes #124783

extensions/markdown-language-features/src/markdownEngine.ts

@@ -67,6 +67,7 @@ interface RenderEnv {
 }
 
 export class MarkdownEngine {
+
 	private md?: Promise<MarkdownIt>;
 
 	private _slugCount = new Map<string, number>();
@@ -129,6 +130,10 @@ export class MarkdownEngine {
 		return md;
 	}
 
+	public reloadPlugins() {
+		this.md = undefined;
+	}
+
 	private tokenizeDocument(
 		document: SkinnyTextDocument,
 		config: MarkdownItConfig,