perf: replace moment with dayjs dependency

This MR replaces the moment dependency with dayjs because it's more lightweight and also recommended as one of the replacements for moment.

A while ago the maintainers of the Moment.js library wrote a blog post concerning the project status of moment. The maintainers consider the moment project a "legacy project in maintenance mode". moment is a large library and this project only uses the fromNow function (except in the webview but that's a different package.json).

Replacing moment with dayjs shouldn't have any negative side-effects, especially because it's only used on one place. It also claims to have a largely Moment.js-compatible API.