FR: LinkedIn Auth Provider

### [REQUIRED] Describe your environment

* Operating System version: Mac OS Catalina
* Browser version: Google Chrome 79
* Firebase SDK version: 7.6.1
* Firebase Product: auth

### [REQUIRED] Describe the problem

#### Steps to reproduce:
1. On the https://console.firebase.google.com, in the section "Authentification" or JS SDK, there is no LinkedIn provider
2. On the https://console.cloud.google.com, in the product "Identity Platform", there is a LinkedIn provider

### A little word

Thanks a lot, Firebase and GCP are very cool to use and take part of our efficiency.