Add ability for institutions to add a librarian chat widget

From Jamboree Trello Board: https://trello.com/c/eDvuCi05

Was determined to be lower hanging fruit from this bigger-scoped enhancement:
Librarians can embed media widgets, search widgets, and other libguides widgets into their institution's GALILEO site.

LibraryH3lp: https://docs.libraryh3lp.com/custom-away

There are TWO MR's on this issue. One was closed. The new one is: !1120 (merged)