Closes #9136

Fixes a bug where users were able to add books without titles by putting only whitespace characters into the required title field.

Technical

Adds a regex check in plugins/openlibrary/js/validate.js to the title class used by templates/books/add.html that ensures the title input contains at least one non-whitespace character.

Testing

1. Go to the 'Add Book' page
2. Attempt to add a book with a title containing only whitespace characters (i.e. matches /\s+/)
3. Observe that the action is not successful and the title input box is red

Screenshot

Stakeholders

@cdrini