extensions/typescript-language-features/src/languageFeatures/completions.ts/MyCompletionItem/getDocumentation
class MyCompletionItem:	private getDocumentation(
		client: ITypeScriptServiceClient,
		detail: Proto.CompletionEntryDetails,
		baseUri: vscode.Uri,
	): vscode.MarkdownString | undefined {
		const documentation = new vscode.MarkdownString();
		Previewer.addMarkdownDocumentation(documentation, detail.documentation, detail.tags, client);
		documentation.baseUri = baseUri;
		return documentation.value.length ? documentation : undefined;
	}