[Tree] Documentation

[Diaan]

Provide a general summary of the issue here

When working on the documentation for this component, please have a look at the review comments that were left on this PR, to have a starting point: #1647

Task

• Usage Tab
• Usage Demo Component
• Code Tab
• A11y Tab

👤 Your name

Diana

🧢 Your Product/Team

No response

[anna-lach]

Please also check a comment from this PR: https://github.com/sl-design-system/components/pull/2018/files/16db3f603584a362f10e880b506ff1fd0b2d48ab#r2077728272