Document support for PHP 7.2 in Changelog

[kbabioch]

Given that there was much discussion about Nextcloud's support of PHP 7.2 before the release (see #7384 #6786), I found it astounding that the official Changelog does not contain any such reference.

This should be added, so people know whether or not they can finally upgrade PHP. Information like this should always be part of the Changelog.

[tflidd]

Good point, you can either make the changes yourself and submit a pull request (https://github.com/nextcloud/nextcloud.com/blob/70d634c05d5c10deb550b0b1fcb8d45051b37b5c/page-changelog.php) or we'll wait for @jospoortvliet

[MorrisJobke]

We have it listed already in the 13 admin docs: https://docs.nextcloud.com/server/13/admin_manual/installation/system_requirements.html#recommended-setup-for-running-nextcloud

The 12 docs state that it is not compatible: https://docs.nextcloud.com/server/12/admin_manual/installation/system_requirements.html#recommended-setup-for-running-nextcloud

Maybe we should add the upper limit as well to not run into the same issues as with 12 some time ago.

[MorrisJobke]

Fixed by nextcloud/nextcloud.com#786