Update documentation styling for easier navigation

[tomvothecoder]

Description

• Closes [Doc]: Improve style and navigation of documentation site #618

Summary of changes

• Update README.rst contributors section
• Add sphinx_design dependency for grid tables
• Update homepage for simple navigation
• Add overview.rst page to move overview content
• Add getting-start-guides/ with sub-nesting of pages for getting started
• Add team.rst with grid of team members
• Update gallery.rst with grid of examples
• Update demos.rst with grid of links
• Update conf.py configuration for sphinx_design grid, custom CSS stylesheet, and custom xarray functions for generating grids
• Update .gitignore

Checklist

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• My changes generate no new warnings
• Any dependent changes have been merged and published in downstream modules

If applicable:

• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass with my changes (locally and CI/CD build)
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have noted that this is a breaking change for a major release (fix or feature that would cause existing functionality to not work as expected)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 100.00%. Comparing base (d0e33aa) to head (28a5af6).

Additional details and impacted files

@@            Coverage Diff            @@
##              main      #624   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           15        15           
  Lines         1588      1588           
=========================================
  Hits          1588      1588           

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[tomvothecoder]

Preview: https://xcdat.readthedocs.io/en/doc-618-doc-style/