src/vs/workbench/services/label/common/labelService.ts/LabelService/registerFormatter
class LabelService:	registerFormatter(formatter: ResourceLabelFormatter): IDisposable {
		this.formatters.push(formatter);
		this._onDidChangeFormatters.fire({ scheme: formatter.scheme });

		return {
			dispose: () => {
				this.formatters = this.formatters.filter(f => f !== formatter);
				this._onDidChangeFormatters.fire({ scheme: formatter.scheme });
			}
		};
	}