feature request: add custom links to default sign-in experience

[nichu42]

What problem did you meet?

The default sign-in flow only allows to add links to terms of use, privacy policy and help, with hard-coded labels.

Describe what you'd like Logto to have

We'd like to add two more links that to assist users who are struggling with the process:

• Documentation / Setup Help
• Account Center (where you can manage your MFA settings)

An option to add 2-3 custom links would solve this issue.