Support appHash for Twilio Verify in signInWithOtp

[themightychris]

This was requested in supabase/auth#1235 but got closed with a note that you can achieve it now with a custom send SMS hook—but it really doesn't need to be that complicated

When using Twilio Verify for SMS login, you have to use their built-in message templates which is what enables you to get up and running instantly without the big waiting period to get compliance cleared for sending custom SMSs. However this means that if you want to take advantage of autofill on Android you need to include your app's unique apphash signature in your request to Twilio Verify so that it can be appended to the SMS content

It would be wonderful if Supabase's signInWithOtp method in dart just had an optional parameter for appHash that would be passed through to the Twilio Verify API call using the existing twilio verify support instead of having to build it custom to take full advantage of twilio verify. Supabase's Twilio Verify integration is already awesome and a great way to get up and running quickly, and with this one small addition of a parameter to pass through we could achieve seamless login with it on Flutter apps