Migrate additional website content

[speth]

Changes proposed in this pull request

This PR transfers most of the remaining version-specific content from the cantera-website into this repository. Specifically, this includes:

• Release notes
• Installation instructions
• C++ compilation and application tutorials
• Glossary

In addition, a new page has been added to the "Develop" section explaining a bit about how the source material for the documentation is organized and some useful syntax for working with MyST, reST, and Doxygen.

If applicable, fill in the issue number this pull request is fixing

Continues work on https://github.com/Cantera/enhancements/issues/178

If applicable, provide an example illustrating new features this pull request is introducing

Checklist

• [x] The pull request includes a clear description of this code change
• [x] Commit messages have short titles and reference relevant issues
• [x] Build passes (scons build & scons test) and unit tests address code coverage
• [x] Style & formatting of contributed code follows contributing guidelines
• [x] The pull request is ready for review

[speth]

Thanks for looking this over, @bryanwweber. I made the suggested changes, which requires re-approval before I can merge.

[codecov[bot]]

Codecov Report

Attention: 16 lines in your changes are missing coverage. Please review.

Comparison is base (fb53e96) 72.74% compared to head (6a056b0) 72.75%. Report is 2 commits behind head on main.

Files	Patch %	Lines
doc/sphinx/userguide/demo1a.cpp	69.23%	4 Missing :warning:
doc/sphinx/userguide/demoequil.cpp	71.42%	4 Missing :warning:
doc/sphinx/userguide/kinetics_transport.cpp	87.87%	4 Missing :warning:
doc/sphinx/userguide/thermodemo.cpp	83.33%	4 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #1657 +/- ## ========================================== + Coverage 72.74% 72.75% +0.01% ========================================== Files 371 375 +4 Lines 56500 56584 +84 Branches 20443 20494 +51 ========================================== + Hits 41100 41168 +68 - Misses 12385 12401 +16 Partials 3015 3015 ```

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[speth]

I mainly have a comment on the location of the demo C++ files. I believe that they should be moved to samples/cxx so they are covered by CI, which will ensure that they are kept up to date. Whether this is done in this PR or a subsequent one is inconsequential, as long as it is taken care of before the release of 3.1.

I was planning on setting these up to run as part of the test suite but forgot before opening this PR. So, rather than wait and risk forgetting to ever do this, it is now implemented. I went with an option that's slightly different from your suggestion, since I only want to include these samples in the C++ Tutorial and not have them repeated in the Examples section, where I think they would distract from the more interesting example programs.