Add banner to library content picker modal

[jmakowski1123]

As an author, I might get confused about why I don't see all my library content from the Library Content Picker modal I need a visual indicator that tells me I am only able to see published content from this modal.

Add a banner that says "Only published content is visible and available for reuse" to the top of the Library Content Picker modal.

[bradenmacdonald]

@jmakowski1123 This is the "course search modal":

You mean the "Library Content Picker modal" right? :)

[bradenmacdonald]

@jmakowski1123 Should this banner be included in Sumac as well?

[jmakowski1123]

Yes, I meant the Library Content Picker modal!

If this is acceptable to get into Sumac, let's aim for that.

[pomegranited]

Another option would be to change the Search box placeholder text to "Search published content" -- if anyone reads that?

[navinkarkera]

@jmakowski1123 @lizc577 @sdaitzman @marcotuts This is ready for AC testing on the sandbox

[sdaitzman]

Looks good to me!

The number of concentric visual containers here (box inside a shadow inside a box inside a box inside a shadow) is a bit visually busy, and worth improving in some future update, but I don't think it needs to be a blocker/priority right now.