Update message that customizing feed content is available within the app onboarding flow for new users.
// This is a sub-task of T141397. //
==== Proposed design
| App onboarding 1 {F10927691} | App onboarding 2 (no sync) {F10927703} | App onboarding 3 {F10927707}
**Design details: **
Essentially the proposal is to amend the app onboarding implemented on T166393 for new users on the Fortune cookie release, whereby the following is updated:
- Onboarding screen 1 description text - update the text to refer to new feed content and the new customization option. //Proposed// description is "Discover interesting articles and content related to your reading on the Explore feed. Easily customize it show favorite sections such as **Random** and **On this day** first."
- Onboarding screen 2 illustration - update the illustration to refer to saving to reading lists and offline (since sync is not yet available)
- Onboarding screen 2 text - update text to refer to saving to reading lists only. //Proposed// title is "Save to reading lists", and //proposed// description is "Create reading lists from articles you want to read later, even when you’re offline."