Introduce Google shared library

[WalkQuackBack]

Is there an existing issue outlining your problem?

• [x] I have searched the existing issues and they do not solve my problem.

Describe your issue.

The shared One Google components across various Google products right now are only themed by the Google userstyle. Some users do not use the Google userstyle considering that it is unmaintained and has many issues.

A Google shared library, theming ogs.google.com and other shared components like header buttons, companion sidebars, and tooltips would reduce deduplication and increase consistency.