Improve docs by mentioning how to adjust token lifetime

[DriesCruyskens]

I can't find any information on how to change token expiration lifetime for Auth0. The only mention of it is this small paragraph: https://hexdocs.pm/ash_authentication/tokens.html#token-lifetime. The docs could be improved by mentioning how to change the lifetime here or in the Auth0 tutorial.

I assumed it is configurable on the Auth0 side but changing the Access token lifetime for the Auth0 Management API in the Auth0 dashboard (mentioned here) does nothing and there are no other mentions of token lifetimes in the Auth0 docs...

It's possible that I'm not seeing a simple solution to this since I am fairly new to ash authentication. I would gladly improve the docs in a PR myself if I knew how to solve this issue. Thanks in advance!