Add notice in editor to direct next steps after selecting course layout

[donnapep]

Is your feature request related to a problem? Please describe

After selecting a layout when creating a new course, it's hard to know what the next step should be if you're a new user. This is especially true when the layout that the user selects is not the default one, as you need to scroll down the page to see the Course Outline block. It's very easy to miss.

Describe the solution you'd like

Display a dismissible info notice in the block editor based on the criteria given below.

Display Criteria

• Notice is triggered when a user creates their first course and after selecting a course layout.
• Notice is no longer displayed as soon as the course contains at least one published lesson.
• Notice is not displayed for subsequent courses the user may create. If there are multiple courses, none of which have lessons, then display the notice on both, but don't show it on any course after lessons have been added to either one.
• Notice is per user.
• If the user dismisses the notice, it's never displayed again.

Link

Clicking the link does 1 of 2 things:

• Focuses the Course Outline block (if it exists on the page), which should be enough to automatically take the user to the block's location in the editor.
• Adds the Course Outline block to the bottom of the editor and takes the user to it.

The goal is to help new users create their first course. There shouldn't be a need to help them create subsequent courses, since presumably by then they're already more familiar with how Sensei works. We also don't want to bother our existing users either.

Describe alternatives you've considered

• Moving the Course Outline block higher up in the layouts. The problem with that option is that it doesn't look so good for some of the layouts and may require tweaks from a design resource.
• Integrating lesson creation with the Course Layout wizard. Although this could be a good option, we'd need to recruit a design resource. This could still be a good option in the future.

Additional context

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[donnapep]

We may not need this. Moving to Blocked.