Automatically open `hub.guardrailsai.com/tokens` url when running guardrails configure

[zsimjee]

          Since this url is static, we could just open it for them.  Thoughts?

Originally posted by @CalebCourier in #652 (comment)

[edwin-pan]

+1 on this, was confused about the token on first install, and there was no mention of a token in the main README. This is actually the first place I found information about what the token is for, though it does point me in the right direction.

[dtam]

@AlejandroEsquivel graciously added this

➜  guardrails configure
Enable anonymous metrics reporting? [Y/n]: Y
Do you wish to use remote inferencing? [Y/n]: Y

Enter API Key below 👉 You can find your API Key at https://hub.guardrailsai.com/keys