src/vs/workbench/api/common/extHostTypes.ts/SnippetString/appendChoice
class SnippetString:	appendChoice(values: string[], number: number = this._tabstop++): SnippetString {
		const value = values.map(s => s.replace(/\$|}|\\|,/g, '\\$&')).join(',');

		this.value += '${';
		this.value += number;
		this.value += '|';
		this.value += value;
		this.value += '|}';

		return this;
	}