docs: 📚 bring back documentation

[mariohamann]

Description

We're documenting how a component works and what it does and which features it offers – not just single attributes!

During our docs migration, there were former docs migrated to templates (instead of the definition that only samples are moved to templates), that are definitely needed for proper documentation to understand how to use the component:

• Media / Description: We need to document how to use descriptions, as this is more or less the only thing what media does and why inverted exists.
• Tab Group / Scrollable: Scrollable is something designers and developers have to be aware of from the documentation. It's part of how it works and they have to do nothing about it.
• Tab Group / Contained: It's worth bringing this into the docs as well. Container is a default feature and therefore has to be shown in context. Move this to sd-tab instead of sd-tab-group. It's more or less the same as for sd-option – it makes not really sense to document sd-option disabled without the surrounding group.´

Where to put the documentation

DoR

• [x] Item has business value
• [x] Item has been estimated by the team
• [x] Item is clear and well-defined
• [x] Item dependencies have been identified

DoD

• [ ] Documentation has been created/updated (if applicable)
• [ ] Migration Guide has been created/updated (if applicable)
• [ ] Relevant stories (Features, A11y) are created/updated
• [ ] Implementation works successfully on feature branch

[Vahid1919]

One the sidenote regarding radio-button template. I believe that was created before we decided to turn all radio/radio-button stories into sd-radio-groups. It was not an intentional choice to add it after the fact. But I see how it is somehow "obsolete" now.