no-implicit-declare-namespace-export
Disallows the use of implicit exports in "ambient" namespaces.
TypeScript implicitly export all members of an "ambient" namespaces, except whether a named export is present.
Invalid:
// foo.ts or foo.d.ts
declare namespace ns {
  interface ImplicitlyExported {}
  export type Exported = true;
}
Valid:
// foo.ts or foo.d.ts
declare namespace ns {
  interface NonExported {}
  export {};
}
declare namespace ns {
  interface Exported {}
  export { Exported };
}
declare namespace ns {
  export interface Exported {}
}