Wizard: Improve template mode selection and Reader theme selection when active theme is also a Reader theme

[westonruter]

Feature description

When a site has a Reader theme already set as the active theme (e.g. Twenty Twenty), when the user expresses they are non-technical then both the Reader mode and the Transitional mode should show as ✅ recommended options.

Additionally, when selecting Reader mode, the list of themes should no longer omit the active theme from the list. Instead, if the user selects the active theme to be the Reader theme, then the template mode should be automatically switched from reader to transitional, and a notice can appear on the summary screen to make them aware of this. Saying something like:

Since you selected a Reader theme which is the same as your site's active theme, you've automatically been switched to Transitional template mode.

---

Do not alter or remove anything below. The following sections will be managed by moderators only.

Acceptance criteria

Implementation brief

QA testing instructions

Demo

Changelog entry