Documentation updates

[speth]

Changes proposed in this pull request

• Add YAML API docs for two-temperature-plasma reaction
• Fix links in TwoTempPlasmaRate constructor
• Provide extended description of derivative_speed.cpp for website
• Clarify rationale for ArrheniusRateBase._cinit
• Describe list-based format for YAML coverage dependencies
• dusty_gas.py requires Cantera 2.6.0

Checklist

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

[codecov]

Codecov Report

Merging #1231 (d5ee2af) into main (cd98c25) will decrease coverage by 0.00%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main    #1231      +/-   ##
==========================================
- Coverage   65.47%   65.47%   -0.01%     
==========================================
  Files         327      327              
  Lines       46349    46350       +1     
  Branches    19688    19688              
==========================================
  Hits        30349    30349              
- Misses      13475    13476       +1     
  Partials     2525     2525              

Impacted Files	Coverage Δ
src/base/AnyMap.cpp	85.12% <0.00%> (-0.08%)	⬇️

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[ischoegl]

Looks good to me (and PR failures are caused by other issues).