Improve UX on Global Styling vs Edit Locations in Getting Started

[jauyong]

Feature description

Priority: Issue

Miro board link Issue 13

Issue 13: https://docs.google.com/spreadsheets/d/1PWNEY5L9neu1O10p2KGczON8_lWOCiXOUeGRFT3wz1k/edit#gid=0

Difficulty understanding where content gets edited vs visual global styles get customized

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Acceptance criteria

1. Make it clear to users they edit global styles in customizer and content in block editor in the getting started as a 1-2-3.
2. Prevent broken preview experiences for new users with demo content in the view they land on.

Implementation brief

QA testing instructions

Demo

Changelog entry

[jwold]

AC 1 is about reviewing the 1-2-3 to identify a simpler way to onboard users.

AC 2 may be a bug, we need to recheck this.