chore: add the preselect store option to readme

[brunodesde1987]

Description

It adds the new preselect store option to the Configuration table with a concise explanation in the description column.

Checklist

• My code follows the style guidelines of this project
• I have performed a self-review of my own changes
• I have run yarn lint to make sure my changes pass all tests
• I have run yarn test to make sure my changes pass all linters
• I have pulled the latest changes from the upstream main branch
• I have tested both the react and the CDN versions on local and integration environments
• I have added the necessary labels to this PR in case a new release needs to be published after merging into main (e.g. release and patch)

Contribution guidelines

For contribution guidelines, styleguide, and other helpful information please
see the CONTRIBUTING.md file in the root of this project.