Allow using IndieAuth.com as an OpenID-2.0 provider

[strk]

I've read that IndieAuth.com can be used as an OpenID provider, but docs show it's only providing OpenID-1.x services. This ticket is to request also providing OpenID-2.x services.

For example, gitea.io does not support OpenID-1.x (http://try.gitea.io) as it uses a Go library also only supporting 2.x+ (yohcop/openid-go#43)

\cc @aaronpk

[strk]

Here's where I see that it only acts as an OpenID-1.x provider: https://indieauth.com/openid