Similar to the Clusters topic, add a topic about configuring multiple
environments. This likely needs some work, the example is a bit
contrivied but at least shows how we can look up attributes, then use
those attributes to look up additional configuration from platform-wide
configuration data.
This commit removes the extra `./platform` argument from any of the
current tutorial/topic docs to reflect the change that was made to
`holos render platform` in version `0.100.0`.
Previously we didn't have good documentation on how to manage multiple
sets of clusters.
This patch adds a clusters topic in the structures category. Each one
of the environments, projects, owners, etc... structures follow the same
pattern as #Clusters and #ClusterSets, so it makes sense to put them
into a dedicated sidebar category for specific CUE structures.
