Add wp-polyfill as dependency to react to fix IE11 bug

[IreneStr]

Summary

This PR can be summarized in the following changelog entry:

• Fixes a bug where the configuration wizard would not load in Internet Explorer 11 when Gutenberg was active.

Relevant technical choices:

• Because IE11 needs wp-polyfill to be registered before react, we add wp-polyfill as a dependency to react. If Gutenberg would do this, this fix can be reverted. I've created a PR on Gutenberg: Add wp-polyfill as dependency to react WordPress/gutenberg#11916.

Test instructions

This PR can be tested by following these steps:

• Follow the steps from the issue.

Quality assurance

• I have tested this code to the best of my abilities
• I have added unittests to verify the code works as intended

Fixes #11597

[afercia]

Trying to recap some testing results:

The fix proposed for Gutenberg in WordPress/gutenberg#11916 makes the Configuration Wizard work correctly but doesn't completely solve our issue because I'm still getting an error for the Analysis WebWorker:

I have no idea why but, as mentioned in the issue, the fact babel-polyfill is imported in js/src/wp-seo-analysis-worker.js might have some implications.

When applying this PR, the error is gone. Worth noting there are other warnings that come from Gutenberg, see WordPress/gutenberg#11918

Lastly, in the WP Dashboard I'm getting this error:

which comes from createNSResolver() used in the yoast-components getFeed.js.

[IreneStr]

The dashboard issue is a known issue: #11073

Let's merge this 😄