Co-authored-by: dylanjameswagner <hello@dylanjameswagner.com>
Co-authored-by: Doug Cone <nullvariable@users.noreply.github.com>

The WordPress 5.4.2 release included an additional change to the way Pantheon manages protected web paths by adding the list explicitly to the pantheon.upstream.yml file. The paths listed in the new location were missing the trailing '/' character, which changed the behavior of the path matching. This amended release restores the missing trailing slashes. No changes to WordPress itself are included.

I recommend removing ```Icon?``` from the gitignore as it matches files and directories in a case-insensitive way named "icons" or "icon1" etc

Use `cache-control: no-cache, no-store, must-revalidate` when on the WordPress admin and logged-in

In Pantheon environments, the standard WordPress update nag is replaced
with one specific to Pantheon. Users on the standard WordPress upstreams
will see "A new WordPress version is available!" while users on a Custom
Upstream will see "A Pantheon Custom Upstream update is available!".

This message only appears when there is a new upstream update available
(no longer when a new WordPress version is released).

The block editor is now in WordPress core; it's not necessary to tweak
the WordPress 4.9 callout anymore.

See #141