Make a Casdoor app example based on Casdoor TOTP

[hsluoyz]

Tech stack:

• React Native
• Facebook Expo: https://expo.dev/
• UI library: https://reactnativepaper.com/

It will first support Casdoor's TOTP: https://casdoor.org/docs/user/multi-factor-authentication/#configuring-multi-factor-authentication-using-a-totp-mobile-app (to scan the code)

But it will also support all general-purpose 2FA scenarios, like Google Authenticator: https://play.google.com/store/apps/details?id=com.google.android.apps.authenticator2&hl=en_US&gl=US

What we already have:

[casbin-bot]

@seriouszyx @ComradeProgrammer @Resulte

[hsluoyz]

Done