fix(typing): Export Multi SAML types

[echojoshchen]

Description

A MultiSamlConfig has a getSamlOptions member, but its type is not exported. Exporting these typings allows TypeScript projects to reference the original definition.

For example:

import { MultiSamlStrategy } from "passport-saml";
import type { MultiSamlConfig, SamlOptionsCallback } from "passport-saml/lib/passport-saml/types";

function getSamlOptions(req: express.Request, done: SamlOptionsCallback): void {
  // Implementation
}
const config: MultiSamlConfig = { getSamlOptions };
const strategy: MultiSamlStrategy = new MultiSamlStrategy(config, verify);

Checklist:

• Issue Addressed: [ ]
• Link to SAML spec: [ ]
• Tests included? [ ]
• Documentation updated? [ ]