update quickstart example code to include provider for 1271 support

[mihoward21]

Both the backend quickstart and the complete app quickstart are missing the provider in the call to verify, meaning no 1271 support. I think it'd be good to include these in any sample code you provide, would help grow support for 1271 in all the apps using siwe. I've come across many apps that don't support it (I assume they just did not think about it, instead of explicitly deciding to not support it).

Not sure if there are other things to do to promote 1271 support, but I think it'd be great for you all to highlight it. Maybe in a future version of the package it could be required by default and users would have to explicitly opt out instead of having to remember to pass in a provider.

[sbihel]

This is a good point. Are there providers that we can reliably point users to, with no set-up required?