The online documentation could have a more appealing/modern look

[fwitte]

I suggest to move away from alabaster or rtd theme, and use furo instead (because I use it for tespy and fluprodia :). We could also think about moving all of oemof's repositories to that template (as far away goal...).

[fwitte]

PR #1131 will deal with this issue. The plan is to leverage the next meeting for an in-person sprint. Instructions to the sprinters:

Preparation

• fork oemof-solph
• clone your fork git clone https://github.com/YOURUSERNAME/oemof-solph
• navigate into the clone cd oemof-solph
• check out the docs/make-style-modern branch git checkout docs/make-style-modern
• In a fresh environment install dependencies pip install -e .[dev]

Contribution workflow

• Change docs source code, create darkmode figures, ...
• Test if renders correctly by running python -m sphinx docs docs/_build from the root of the clone
• Open the index.html page from your docs/_build/ path
• Check result
• Commit changes if happy
• With all commits pushed: Open PR on https://github.com/oemof/oemof-solph with target branch docs/make-style-modern