Kirigami Addons tutorial

To test this MR:

git clone https://invent.kde.org/documentation/develop-kde-org.git
cd develop-kde-org
git switch work/thiagosueto/mobileform
hugo server

You can view the up-to-date state of the tutorial here: https://kdocs.rabbitictranslator.com/kirigamiaddons/public/docs/getting-started/kirigami/addons-introduction/

This tutorial was updated to use snippet and to match up-to-date FormCard.

I'll add CategorizedSettings and other components in a later MR.

Closes #132 (closed)