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.