README sphinx website generation

[clintonsteiner]

• Made significantly easier and still used sphinx

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Notes:

• This simpler approach than create base for readthedocs sphinx site #764 works as long as we choose to stick with a single page of documentation. If we e.g. wanted to render the change log and contribution guide as part of the documentation pages, the approach drafted in create base for readthedocs sphinx site #764 should be used instead.
  – @akaihola 2024-11-16

[akaihola]

Could we try this once in this branch just to see that it works, and then revert back to - master before merging?

[akaihola]

Just to be sure, so this is going to publish the documentation at https://akaihola.github.io/darker?