Implement JOSS doc suggestions

[jschepers]

We implemented the doc suggestions from the JOSS review and fixed/modified some things on the way.

Changes related to the review:

• Quickstart page: We added a short introduction about which ingredients are needed for a simulation. Hopefully, the given tip is more useful now given the context,

• Simulate ERPs page: We added an introductory paragraph to explain the contexts of ERP components and give an example.

• Poweranalysis page: We split "poweranalysis" in two words and matched sidebar and page title.

• Reference Section:

  • We changed the word in the README from "component" to "simulation ingredient" to avoid the overloading of "component".
  • We matched the sub-titles from the sidebar and the titles of the pages.
  • We reordered the sub-sections of the reference section to match the order from the overview page.
  • We added a page about "Experimental design types" with a description about the design types that are currently implemented.

• API/DocStrings:

  • We removed some unintended empty lines between the simulate() docstring and the function such that it is recognized as a doc string.
  • We added some information to the SingleSubjectDesign() and the MultiSubjectDesign() docstrings.
  • We fixed the formatting of the predef_eeg() doc string.
  • We added a reference for the different colours of noise on the reference page "Overview: Noise types".
  • We corrected the spelling of "Artifact.jl" in the RealisticNoise() docstring
  • We added more explanation to the ExponentialNoise() docstring.

• General changes

  • We tried to match all sub-title in the sidebar with the page titles.
  • We added an introductory sentence to all pages.

Additional changes:

• We added the UnfoldSim logo to the documentation page.
• We wrapped the package imports in collapsible setup blocks.

[behinger]

very nice & well done. These are the only two things I noticed

[jschepers]

Dear @roualdes,

thanks again for your detailed list of suggestions. They were really helpful. We revised the documentation accordingly (see the description above). You can find a preview of the changes here: https://unfoldtoolbox.github.io/UnfoldSim.jl/previews/PR101/
Please let us know if your suggestions were sufficiently addressed or if anything is still missing.

Best,
Judith