[DOC] reshuffle of contributing

[story645]

PR summary

Attempt to address hierarchy issues from #28005 by reordering so that:

on contributing page:

• moved the "why should I contribute" into a default open dropdown so that it can both stand out for the folks who need it and can be collapsed for folks who don't.
• code/docs/community contributions get moved under get-started as sub headings
• issue related blocks get shifted into their own section
• removed double nesting on 'codespaces workflow section'
• slight reordering of contributing section

And on the index page:

• removed 'good-first-issues' from index page b/c it's always felt kinda weird anyway and it's a special case of claiming issues
• changes buttons as discussed in DOC: Move bug reports and feature requests to top of contributing index #28011 (comment)
• broke up preamble so "everything is contributing" is at top, and roadmapping/get more involved is after the submit block.

~I haven't built yet, this is very much sketchy. ~

PR checklist

• "closes #0000" is in the body of the PR description to link the related issue
• new and changed code is tested
• Plotting related features are demonstrated in an example
• New Features and API Changes are noted with a directive and release note
• Documentation complies with general and docstring guidelines

[timhoffm]

I feel just the nouns are too terse. What do the mean? Read documentation, write documentation? Documentation of the project or documentation on contributing?

"Contribute code" and "Write documentation" weren't too bad. "Join the community" could be the third one. Alternatively, "Work on code", "Work on documentation", "Work with the community".

[story645]

updated to build community -stuff like citations and adding to the third party list are part of building our community/ecosystem.

[story645]

so the triplet becomes: contribute code, write documentation, build community. I'd use a different verb on code but write code and write docs is clunky in its own way.

[timhoffm]

I find this slightly off: I believe many contributions start because people have a certain idea or problem they are interested in. I assume it's rather uncommon that people say "Oh I want to work on Matplotlib. What can I do?"

I have no good alternative suggestion yet. Just saying the current phrasing is tailored to a rather edge case.

[story645]

I get you, not sure claim is any better...it's the 'navigate the issue tracker' bullet, :hmm:

[story645]

"how do I work on issues" maybe?

[timhoffm]

"how do I work on issues" maybe?

Yes, or "How to work on issues".

[story645]

So I have "Work on an issue" inside contributing.rst, but I think on index we want to keep the FAQ type structure here?