Bring back missing docs

[olayway]

From @rufuspollock:

https://github.com/datahubio/docs is private and unused. Initially was source for datahub.io/docs but that is now ...

https://github.com/datahubio/datahub-cloud-template-dataset/tree/main/docs

I note that https://github.com/datahubio/docs is a small amount of datahub v3 docs plus mostly old v2 docs which were updated in v2.5 / v3a (from 2023)

We have a copy or original v2 docs here https://github.com/datahubio/datahub-v2-docs

And somewhere in datahub-next repo we have the updated version of this from pre v3 release.

[olayway]

@rufuspollock, @Daniellappv I have resurrected the old datahubio/docs which is now the source of https://datahub.io/docs

Important updates:

• old main branch of datahubio/docs archived to v2 (https://github.com/datahubio/docs/tree/v2)
• datahubio/docs visibility changed to public
• /docs folder from datahubio/datahub-cloud-template-dataset repo moved to /DataHub Cloud folder on the main branch of datahubio/docs repo
• Daniela's custom.css copied over to the root
• config.json file added in the root to enable sidebar and edit this page link (but maybe unnecessarily?)
• used contentInclude field in the config.json to show only DMS, DataHub Cloud and Core Data docs for now (can be easily adjusted here: https://github.com/datahubio/docs/blob/8509597822be71b8acbde279e6b8c4435a8dc1b0/config.json#L4)
• adjusted the main README with very basic markdown showing links to the above 3 parts of the docs
• uppercased main subfolders
• added temporary redirects for /docs/dms/:path to /docs/DMS/:path (related to the point above)

Note: I'm not sure about the currently included content - is all DMS related stuff still relevant? Do we want to show Core Data at all? Do we want to unhide any other stuff? Etc.

[olayway]

I've just noticed some broken images but I'm fixing this

[olayway]

I've just noticed some broken images but I'm fixing this

Done

[rufuspollock]

Great job.

uppercased main subfolders

Any reason for this especially? usually we keep lowercase?