[ext.pages] Fix missing current_page assignment, add page indicator update in goto_page

[krittick]

Summary

This adds the missing current_page assignment in goto_page(), and also adds functionality to update the page indicator (if displayed) when goto_page() is used.

Closes #741

Checklist

• If code changes were made then they have been tested.
  • I have updated the documentation to reflect the changes.
• If type: ignore comments were used, a comment is also left explaining why
• This PR fixes an issue.
• This PR adds something new (e.g. new method or parameters).
• This PR is a breaking change (e.g. methods or parameters removed/renamed)
• This PR is not a code change (e.g. documentation, README, typehinting, examples, ...)