Add external link in pages details modal

[Maskoe]

Changes

I noticed the details pages modal does not let me navigate to the external link like the dashboard top pages section lets me do.
So I added it to the modal too.

The code is mostly taken from "assets/js/dashboard/stats/reports/list.js" and minimally adjusted.
This guy noticed it too. https://feedback.plausible.io/267

Tests

• This PR does not require tests

Changelog

• Entry has been added to changelog

Documentation

• This change does not need a documentation update

Dark mode

• The UI has been tested both in dark and light mode

[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.
_{You have signed the CLA already but the status is still pending? Let us recheck it.}