src/vs/editor/contrib/linesOperations/browser/linesOperations.ts/JoinLinesAction/constructor
class JoinLinesAction:	constructor() {
		super({
			id: 'editor.action.joinLines',
			label: nls.localize('lines.joinLines', "Join Lines"),
			alias: 'Join Lines',
			precondition: EditorContextKeys.writable,
			kbOpts: {
				kbExpr: EditorContextKeys.editorTextFocus,
				primary: 0,
				mac: { primary: KeyMod.WinCtrl | KeyCode.KeyJ },
				weight: KeybindingWeight.EditorContrib
			}
		});
	}