Shadow Help Center styles in wp-admin and Gutenberg

[alshakero]

Proposed Changes

This wraps the Help Center in a shadow root to prevent styles from leaking in and out of the Help Center.

Why are these changes being made?

The Help Center styles can break a few things and be broken by a few things because the Help Center runs in many places under several environments.

Testing Instructions

1. In apps/help-center run yarn dev --sync.
2. Test in wp-admin/post-new.php and wp-admin.
3. Make sure every route of the Help Center is well-styled.

Next

Once this is live. We can merge this

[github-actions]

Calypso Live (direct link)

https://calypso.live?image=registry.a8c.com/calypso/app:build-117927

Jetpack Cloud live (direct link)

https://calypso.live?image=registry.a8c.com/calypso/app:build-117927&env=jetpack

Automattic for Agencies live (direct link)

https://calypso.live?image=registry.a8c.com/calypso/app:build-117927&env=a8c-for-agencies

[matticbot]

Here is how your PR affects size of JS and CSS bundles shipped to the user's browser:

Async-loaded Components (~240 bytes added 📈 [gzipped])

name                               parsed_size           gzip_size
async-load-automattic-help-center       +627 B  (+0.1%)     +240 B  (+0.1%)

React components that are loaded lazily, when a certain part of UI is displayed for the first time.

Legend

What is parsed and gzip size?

Parsed Size: Uncompressed size of the JS and CSS files. This much code needs to be parsed and stored in memory.
Gzip Size: Compressed size of the JS and CSS files. This much data needs to be downloaded over network.

Generated by performance advisor bot at iscalypsofastyet.com.

[matticbot]

This PR modifies the release build for the following Calypso Apps:

For info about this notification, see here: PCYsg-OT6-p2

• blaze-dashboard
• command-palette-wp-admin
• help-center
• notifications
• odyssey-stats
• whats-new

To test WordPress.com changes, run install-plugin.sh $pluginSlug fix/help-center-in-shadow on your sandbox.

[alshakero]

Since styles are shadowed now, we lost the styles of the Help Button.

Fixed.

[escapemanuele]

I see this in /wp-admin

[renancarvalho]

Great changes!
I have tested many routes desktop, mobile, wp-admin. All worked fine. Haven't seen anything off or wrong.
🚀

[escapemanuele]

Tested wp-admin and the editor and I didn't find any issue!