feat: implement dynamic last updated phrase

[anxkhn]

Description:
This PR improves the UI by dynamically displaying the last data update time based on the latest commit to the /data directory, rather than the hardcoded updated "weekly” text.

Since this repository hasn’t been updated in a while, the previous static label could be misleading. The new implementation fetches the timestamp of the latest commit via the GitHub API and formats it into a human-readable “time ago” phrase (e.g., updated 3 days ago), making the displayed information more accurate and useful.

Changes:

• Added fetchLastUpdatedPhrase() to script.js to retrieve the last commit date from GitHub API.
• Implemented formatTimeAgo() utility to convert timestamps into a relative and nice human readable format.
• Updated index.html to replace the static span with an element that can be dynamically updated.

Pre-commit Checks:

• All pre-commit hooks have been run locally with pre-commit run --all-files.
• No linting or formatting issues were found.

UI Design and Aesthetics:

• Matches the existing design style with the same font and green color scheme.
• Minimal changes to DOM structure for seamless integration.

Screenshot: