Valid Threads username with dot not working

[celiamgtt]

Description
Error "data: Expected valid Threads username: @username" when using a Threads username with dots inside.

To Reproduce
Steps to reproduce the behavior:

1. Go to https://itch.io/user/settings
2. Click on "more links"
3. Add a Thread username with a dot (example lya.mgtt)
4. Error displayed: Expected valid Threads username: @username

Expected behavior
Threads username with dots should be accepted.

Screenshots

Desktop (please complete the following information):

• OS: macOS
• Browser: Chrome