src/vs/workbench/contrib/customEditor/browser/customEditors.ts/CustomEditorService/registerCustomEditorCapabilities
class CustomEditorService:	public registerCustomEditorCapabilities(viewType: string, options: CustomEditorCapabilities): IDisposable {
		if (this._editorCapabilities.has(viewType)) {
			throw new Error(`Capabilities for ${viewType} already set`);
		}
		this._editorCapabilities.set(viewType, options);
		return toDisposable(() => {
			this._editorCapabilities.delete(viewType);
		});
	}