Create the options-page subpage when the docs dev shell is loaded.
Also simplify the dev shell definition by just utilizing what's in configurePhase of the docs derivation
Renders the documentation for clanServices. Options for the modules are
extracted and rendered the same way as for the existing clanModules.
Additionally tweaks the typography for the documentation of options
slightly
This is a good idea, to make lib agnostic from clan-core
The next step could be to rename the clan-core argument name
Or to explizitly pass the actual dependencies, instead of everything in
clan-core
Some test were referring to the whole source code via ${self} which amde them rebuild on every single commit.
This is not mitigated by introduceing `self.filter { include = [...]; }` allowin to a content addressed subset of the source code in tests.
Currently, important tools from the default shell are lost as soon as select-shell is used to switch to another shell. select-shell itself, for example is missing, which makes it impossible to switch back to another shell.
