app classic Blade-PHP view: Re-add markup

The app classic Blade-PHP view had some markup missing, this is re-added in this release.
c71e3a8

This release also updates and cleans up a few files based on latest Sage 10.
The code for the addition of editor styles is simplified.

`acorn` >=`4.2.0`: Inverted FSE/(classic) Blade-PHP template files priority

With acorn 4.2.0 the priority of FSE and (classic) Blade-PHP template files was inverted, mirroring the previously used, patched acorn.

`acorn` >=`4.1.0` native FSE support

This release/milestone uses the latest acorn 4.1.0 (and associated Sage 10 theme),
which introduces direct FSE support. In contrast to the previously used, patched acorn,
the new acorn 4.1.0 FSE support has an inverted template file priority handling:
(Classic) Blade-PHP template files override FSE template files.
This rather small but important detail has to be taken into account when making a hybrid FSE theme
(one that uses FSE and (classic) Blade-PHP template files, e.g. for plugins that do not support FSE/shortcodes yet).

The README has been updated with an detailed explanation and details.