[DOCS] Cleaning up the User Guide

[erikvansebille]

Description

This PR cleans up the user guide on the docs.parcels-code.org page. in particular, it moves the Getting Started section into the User Guide itself, so that everything is in one place. It also adds some clarifying wording, removes the (duplicate) installation-instructions on the v4 page and adds anchor links to the headings on the User Guide

Checklist

• Supports Updating parcels website and documentation for v4 preview release #2702
• This PR targets the correct branch (main for normal development, v3-support for v3 support)

AI Disclosure

• This PR contains AI-generated content.
  • I have tested any AI-generated content in my PR.
  • I take responsibility for any AI-generated content in my PR.
  • Describe how you used it (e.g., by pasting your prompt): Creating custom css for adding anchors to the headers that don't show up in the side-bar

[VeckoTheGecko]

Could you elaborate on what this does? Which anchor tags were you having problems with? I think it would be better to work within the pydata-sphinx theme we're using rather than adding custom CSS (as its more difficult to maintain)

[erikvansebille]

Yes, I added the custom CSS because I wanted both headers on the main page (that could be anchored so we could directly link to a section) as well as a table-of-content in the left side-bar. See screenshot

Without this custom css, the headers would appear twice in the main body, see orange circles in the screenshot below

I asked an LLM how to do this and after a lot of back-and-forth this was the solution it came up with. If you have a better idea, then I'd be curious to hear!

[VeckoTheGecko]

I misunderstood your original message here. I don't know if there's a way to do this without custom css

I'll leave it up to you, but just wanted to flag dabbling in custom css does add an additional maintenance burden

[VeckoTheGecko]

Changes look good. Just a question about the custom css