Added the constructor defination on OAuthProvider (#1673)

Author: wti806

packages/auth-types/index.d.ts

@@ -182,6 +182,7 @@ export interface IdTokenResult {
 }
 
 export class OAuthProvider implements AuthProvider {
+  constructor(providerId: string);
   providerId: string;
   addScope(scope: string): AuthProvider;
   credential(idToken?: string, accessToken?: string): OAuthCredential;

packages/firebase/index.d.ts

@@ -3173,6 +3173,7 @@ declare namespace firebase.auth {
    * @param providerId The associated provider ID, such as `github.com`.
    */
   class OAuthProvider implements firebase.auth.AuthProvider {
+    constructor(providerId: string);
     providerId: string;
     /**
      * @param scope Provider OAuth scope to add.