[Improvement] Allowed type files are not indicated

[ingridusta]

Prerequisites

• I understand and accept the project's code of conduct.
• I have already searched in existing issues and found no previous report of this bug.

Describe the bug and add attachments

1. Contact-us page is displayed
2. File types allowed are not indicated to the user (for both hummingbird and classic themes)

Expected behavior

1. Contact-us page is displayed
2. File types allowed are indicated to the user (improvement)

Steps to reproduce

1. Go on contact-us page
2. Check the type file allowed

PrestaShop version(s) where the bug happened

dev branch

PHP version(s) where the bug happened

No response

Your company or customer's name goes here (if applicable).

No response