[FEATURE] Documentation update

[davidorme]

Description

This PR is for the feature/docs-ui-update branch, which is being used to collect changes to the documentation before rolling it out officially to develop. The intention is to stop the main site content (which follows develop) from jigging around all over the place while people are trying to use it and provide a single stable update.

Summary of issues merged in here:

• Swapping to pydata-sphinx-theme
• Adding a DataTables version of the variables table: searchable and filterable.
• Implementation section renamed to Science, and restructured to make it easier to find the scientific content of the models
• Removed developer focused content out of the Users section (where it just confuses people) into the Developers section
• Structured the sidebar of the Users documentation pages to highlight the tutorials primarily, with reference materials at the bottom grouped into a couple of subheadings

Important

• This PR is being built here: https://virtual-ecosystem.readthedocs.io/en/feature-docs-ui-update/
• This PR branch requires merges to add new content. PRs onto this branch have a reduced set of tests that need to pass (docs, pre-commit, and one test). The branch will need to pass the full suite when we merge into develop, but this reduces the overhead for a PR of largely docs based changes.
  If you are creating a branch on an issue to bring in here remember to change the target branch from develop

Will close #1248

Type of change

• New feature (non-breaking change which adds functionality)
• Optimization (back-end change that speeds up the code)
• Bug fix (non-breaking change which fixes an issue)

Key checklist

• Make sure you've run the pre-commit checks: $ pre-commit run -a
• All tests pass: $ poetry run pytest

Further checks

• Code is commented, particularly in hard-to-understand areas
• Tests added that prove fix is effective or that feature works
• Relevant documentation reviewed and updated

[codecov-commenter]

Codecov Report

❌ Patch coverage is 0% with 68 lines in your changes missing coverage. Please review.
✅ Project coverage is 94.10%. Comparing base (2dd731e) to head (7f9193c).

Files with missing lines	Patch %	Lines
virtual_ecosystem/core/docutils.py	0.00%	68 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #1250      +/-   ##
===========================================
- Coverage    94.95%   94.10%   -0.85%     
===========================================
  Files           71       72       +1     
  Lines         7536     7604      +68     
===========================================
  Hits          7156     7156              
- Misses         380      448      +68     

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