fix: correctly re-export mapping (#259)

Author: OrKoN

src/index.ts

@@ -12,7 +12,7 @@ export * from './gen/main.js';
 export * from './gen/permissions.js';
 export * from './gen/web-bluetooth.js';
 
-export type {CommandMapping} from './gen/mapping.d.ts';
+export type {CommandMapping} from './gen/mapping.js';
 
 type ExternalSpecCommand<T> = {
   // id is defined by the main WebDriver BiDi spec and extension specs do