update SDK_VERSION to the latest value in firebase/app

[Feiyang1]

Fixes #4235

firebase.SDK_VERSION may not be up to date because the value is set at compile time in @firebase/app, which is not necessarily published with every release. This change updates firebase.SDK_VERSION to the latest version of firebase package.

Note that the solution will NOT work if you import scoped packages.
You should import using the umbrella package:

import firebase from 'firebase/app';
firebase.SDK_VERSION; // the latest version

// DON'T do it if you want the latest SDK VERSION
// import firebase from '@firebase/app';
// firebase.SDK_VERSION; // might be a stale version

To fix the issue for the scoped package, we will need to publish @firebase/app with every release to make sure SDK_VERSION is up to date. We need to create a process to automatically add a changeset for @firebase/app for every release.

Since using the umbrella package to import firebase is the recommended way of doing things and all our guides and snippets use the umbrella package, this fix should be sufficient for now and will work for the majority of our users.

[changeset-bot]

🦋 Changeset detected

Latest commit: f6218af

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 5 packages

Name	Type
firebase	Patch
@firebase/rules-unit-testing	Patch

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR

[google-oss-bot]

Size Analysis Report

Affected Products

No changes between base commit (da7f7ff) and head commit (064a660).

Test Logs

• Base (da7f7ff6): https://github.com/firebase/firebase-js-sdk/actions/runs/481401398
• Head (064a6603): https://github.com/firebase/firebase-js-sdk/actions/runs/484095549