9.0.0-beta.4 released

[Feiyang1]

9.0.0-beta.4 has been released with the following changes:

• Added a submodule firebase/messaging/sw to expose messaging service worker APIs. Previously it was only available through the scoped package @firebase/messaging/sw.
• Added API initializeAnalytics() to firebase/analytics to allow you to configure gtag on initialization.
• Fixed Firestore get() returns "Could not reach Cloud Firestore backend" error #4993

[Feiyang1]

Unfortunately 9.0.0-beta.4 is affected by #5018. We need to do a regular release (v8 release) to publish the fix in @firebase/component before we can include it in a new beta release, which is scheduled to happen on Thursday.

Before then, please use 9.0.0-beta.2 if you are being blocked by the issue. Sorry!