Books whose names have accents, generate slugs with errors #1765

Describe the bug
Books whose names have accents, generate slugs with accents and a 404 error occurs when trying to access them

Steps To Reproduce
Steps to reproduce the behavior:

1. Go to a Shelve
2. Click on New Book
3. Name it with something like "Canción" and save it.
4. Try to access to the new book and you going to get an 404 error.

Expected behavior
Book correctly showed.

Your Configuration (please complete the following information):

• Exact BookStack Version (Found in settings): v0.27.5
• PHP Version: 7.3
• Hosting Method (Nginx/Apache/Docker): Nginx