Add Eclipse Tahu as a compatible product

We need to add Eclipse Tahu to the list of compatible products since it is the implementation used for ratification. There is no need to obtain a "Get Listed" request from the project team to do so since the spec committee ratified the spec.

Tahu should be listed in the "Compatible Software" category.

The logo is already available in the PMI: https://projects.eclipse.org/projects/iot.tahu

When clicked, the tile should lead to https://github.com/eclipse/tahu.

Thank you!