Version:

• listmonk: [eg: v2.4.0]
• OS: [e.g. Fedora]

Description of the bug and steps to reproduce:
Trying to upload filetype JPG which is not accepted. Changed to jpg after which the filetype is accepted. Some picture applications generate images with filetypes in capitals (like synology Photo Backup)

Screenshots:
If applicable, add screenshots to help explain your problem.