extensions/markdown-language-features/src/tableOfContentsProvider.ts/TableOfContentsProvider/getHeaderLevel
class TableOfContentsProvider:	private static getHeaderLevel(markup: string): number {
		if (markup === '=') {
			return 1;
		} else if (markup === '-') {
			return 2;
		} else { // '#', '##', ...
			return markup.length;
		}
	}