src/vs/base/common/htmlContent.ts/MarkdownString/_escape
class MarkdownString:	private _escape(value: string, ch: string): string {
		const r = new RegExp(escapeRegExpCharacters(ch), 'g');
		return value.replace(r, (match, offset) => {
			if (value.charAt(offset - 1) !== '\\') {
				return `\\${match}`;
			} else {
				return match;
			}
		});
	}