Missing menu items in the Documentation page.

[Geogouz]

In the Welcome to Rucio's documentation page, I see links towards pages that are not currently available in the left vertical menu. Such an example is the Contributing guide which does not appear in the left menu. Shouldn't we include there any links available in the page?

[rdimaio]

In theory I think this will be hard to keep in sync unless we autogenerate most of the sidebar, like here

documentation/website/sidebars.json

Line 51 in 14db9d8

"items": [{"type": "autogenerated", "dirName": "developer"}]

For the contributing guide in particular, I would propose that we move it to the developer folder and then it will be automatically placed in the sidebar from there