message: `REGISTRATION_CUSTOM_FIELDS` doc improvement
  Improved the docs by being more clear that the env variable accepts a comma-separated value
diff: @@ -106,7 +106,7 @@ User's password is checked against [Pwned Passwords](https://haveibeenpwned.com/
  ### `REGISTRATION_CUSTOM_FIELDS`
  -Let user add data on registration.
  +Comma separated list of custom fields that can addded to registration.
  **Example**
  