usePublicVapidKey not defined in firebase.messaging namespace, causing build error

[jenperson]

[REQUIRED] Describe your environment

• Operating System version: Mac OS 10.13.3
• Firebase SDK version: 10.4.1
• Firebase Product: Messaging (auth, database, storage, etc)

[REQUIRED] Describe the problem

Steps to reproduce:

Steps to Reproduce the bug:

1. Set up Firebase web app using Typescript for FCM
2. Try to call messaging.usePublicVapidKey("key_here1234");
3. Get error: [ts] Property 'usePublicVapidKey' does not exist on type 'Messaging'.

Relevant Code:

Define usePublicVapidKey in firebase.messaging namespace
https://github.com/firebase/firebase-js-sdk/blob/master/packages/firebase/index.d.ts#L464

[abeisgoat]

Looks like it's declared correctly in @firebase/types-messaging but didn't make it to the firebase package's index.d.ts so we just need to move that over.

[jshcrowthe]

Thanks for the report @jenperson and the fix @AbeHaskins this'll go out in the next release 😄