website/integrations: add mailcow (#13727)

* Add mailcow to Applications

* Update wording and layout

* Update website/integrations/services/mailcow/index.md

Co-authored-by: Tana M Berry <tanamarieberry@yahoo.com>
Signed-off-by: Ben <bmfk_m@yahoo.de>

* Update website/integrations/services/mailcow/index.md

Co-authored-by: Tana M Berry <tanamarieberry@yahoo.com>
Signed-off-by: Ben <bmfk_m@yahoo.de>

* Update website/integrations/services/mailcow/index.md

Co-authored-by: Tana M Berry <tanamarieberry@yahoo.com>
Signed-off-by: Ben <bmfk_m@yahoo.de>

* lint

---------

Signed-off-by: Ben <bmfk_m@yahoo.de>
Co-authored-by: Tana M Berry <tanamarieberry@yahoo.com>

website/sidebarsIntegrations.js

@@ -27,6 +27,7 @@ module.exports = {
                         "services/espoCRM/index",
                         "services/hedgedoc/index",
                         "services/kimai/index",
+                        "services/mailcow/index",
                         "services/mastodon/index",
                         "services/matrix-synapse/index",
                         "services/mautic/index",