Adding GitHub to sponsors page

[isaacgsmith]

Description

Adds GitHub to sponsors page of the documentation and alphabetizes the page.

Motivation and context

Closes #1621

How has this been tested?

• Testing pipeline.
• Other.
  Documentation built locally.

Examples

Type of change

• Bug fix.
• New feature.
• Breaking change.
• None of the above.

Checklist

• My change requires a change to the documentation.
  • I have updated the documentation accordingly.
  • (optional) I have built the documentation on my fork following the instructions.
• I have assigned and requested two reviewers for this pull request.

[github-actions]

Before a PR is accepted, it must meet the following criteria:

• Is the necessary information provided?
  • Does the PR have a complete description? Does it explain what the PR is attempting to do/fix, does it explain how it does this?
  • Is there an explanation of why this PR is needed?
  • Please use the TARDIS PR template
• Is this a duplicate PR?
  • If a new PR is clearly a duplicate, ask how this PR is different from the original PR?
  • If this PR is about to be merged, close the original PR with a link to this new PR that solved the issue.
• Does it pass existing tests and are new tests provided if required?
  • The test coverage should not decrease, and for new features should be at or very close to 100%.
• Is the code properly documented?
  • If this modifies existing code, then the docs should be updated. If this adds a new feature, additional documentation should be created.
  • Sphinx and docstrings in the code (in numpydoc format)
• Does this conform to PEP 8 and the TARDIS style guidelines?
• Does the PR fix the problem it describes?
  • Make sure it doesn’t e.g. just fix the problem for a specific case
  • Is this the best way of fixing the problem?
• Is the code tidy?
  • No unnecessary print lines or code comments

[codecov]

Codecov Report

Merging #1622 (fce65b7) into master (267906d) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1622   +/-   ##
=======================================
  Coverage   67.20%   67.20%           
=======================================
  Files          73       73           
  Lines        6150     6150           
=======================================
  Hits         4133     4133           
  Misses       2017     2017           

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[andrewfullard]

I know this is out of scope, but it would be nice to have links to the sponsor's web pages when the logos are clicked.