Folders in updates/ are sorted __semantically__. The separate update classes in each folder are sorted __alphabetically__.

5.10 is higher than 5.2 semantically.

`update_447.php` is higher than `update_446.php` alphabetically.

`update_20211010.php` is higher than `update_20211009.php` alphabetically.

ISO standard date can be sorted alphabetically.

At each major and minor release, a new folder must be created in this folder with the new version number (omitting patch version, which is assumed to be zero).