Display "Last updated"

[unknwon]

Describe the feature

Display the last updated time for the page.

Describe the solution you'd like

The time is displayed in RFC3339 format:

• For a local directory target, use the last modified time of the file.
• For a Git repository target, use the last changed time in Git history.

The frontmatter should also be able to allow user-defined last_updated_at.

Describe alternatives you've considered

n/a

Additional context

No response

Code of Conduct

• I agree to follow this project's Code of Conduct