Create themes for olivero/claro and olivero/gin

Problem/Motivation

At the moment only the default SkipTo themes are available for styling. None of the themes is 100% in line with the styling used for Olivero, Claro, and/or Gin.

Steps to reproduce

Proposed resolution

Come up with proper styling for two themes and then create issues upstream as suggested on https://skipto-landmarks-headings.github.io/page-script-5/config.html:

If you would like a theme added for your organization, please file an issue with the desired colors

Remaining tasks

User interface changes

API changes

Data model changes