Describe the bug
Uploading an image with filename Screenshot 2020-08-04 at 21.42.34.png returns an error.
Uploading an image with filename Screenshot 2020-08-04 at 214234.png succeeds.

Steps To Reproduce
Steps to reproduce the behavior:

1. Edit a page
2. Click on the image icon in the WYSIWYG editor
3. Try to upload an image with the filename above
4. See error

Expected behavior
Uploading an image with dot(s) in filename succeeds.

Screenshots

Screenshot is in French: "file must have only one filename extension"

Your Configuration (please complete the following information):

• Exact BookStack Version (Found in settings): 0.29.3
• PHP Version: 7.3.17
• Hosting Method (Nginx/Apache/Docker): Docker