extensions/markdown-language-features/src/preview/documentRenderer.ts/MdDocumentRenderer/extensionResourcePath
class MdDocumentRenderer:	private extensionResourcePath(resourceProvider: WebviewResourceProvider, mediaFile: string): string {
		const webviewResource = resourceProvider.asWebviewUri(
			vscode.Uri.joinPath(this.context.extensionUri, 'media', mediaFile));
		return webviewResource.toString();
	}