Support Fragment +888 anonymous numbers

[vanyasem]

Is your feature request related to a problem? Please describe.
On the login page you have to choose the country code of your phone number.
Unfortunately the support for Fragment phone numbers is missing (country code +888). They are supported in every official Telegram client.

Describe the solution you'd like
Add +888 to the list of allowed country codes. This would be the best solution, but it's problematic because the library used for phone number input uses a list of countries from https://github.com/stefangabos/world_countries and does not allow additions or modifications by default. It's possible to fork the library ofc.

Describe alternatives you've considered
Allow arbitrary country code inputs to avoid such issues in the future in case a new country code appears and the list isn't yet updated. It's also problematic, as the library used for phone number input doesn't seem to support that.
I'd suggest using a different library.

Additional context
The country name used for +888 in official Telegram clients is "Anonymous Numbers", i.e. Telegram Desktop: