Fix TypeScript error TS2742

Author: ehmicky

src/main.d.ts

@@ -79,3 +79,4 @@ export type { CommonInfo } from './plugins/info/main.js'
 export type { CustomClass } from './subclass/custom.js'
 export type { CreateSubclass, ErrorSubclassCore } from './subclass/create.js'
 export type { NormalizeError } from './subclass/normalize.js'
+export type { SpecificErrorClass }

src/subclass/create.d.ts

@@ -132,6 +132,14 @@ interface ErrorSubclassCore<
 
 /**
  * Error class, with specific `props`, `custom`, etc.
+ *
+ * @private This type is private and only exported as a temporary workaround
+ * for an open issue with TypeScript. It will be removed in a future release.
+ * See:
+ *
+ * - [modern-errors issue #35](https://github.com/ehmicky/modern-errors/issues/35)
+ * - [modern-errors issue #18](https://github.com/ehmicky/modern-errors/issues/18)
+ * - [TypeScript issue #47663](https://github.com/microsoft/TypeScript/issues/47663)
  */
 export type SpecificErrorClass<
   PluginsArg extends Plugins,