Add docs pages for 2025 projects

[khaeru]

This PR adds docs pages for fifteen (15) projects mentioned in the 2025-01 projects overview (internal link) that were not so far mentioned anywhere in the MESSAGEix(-GLOBIOM) documentation.

We could expand this PR to:

• Update CODEOWNERS making the designated LM of the respective project the owner of the documentation page.
• Accept direct commits or PRs into this branch to populate the pages, all currently empty. This could be, initially, a transcription of the slide contents.

How to review

TBD, see above.

• View the preview build of the docs and confirm the project title is spelled and capitalized correctly.

PR checklist

• Continuous integration checks all ✅
• Add or expand tests; coverage checks both ✅
• Add, expand, or update documentation.
• Update doc/whatsnew.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 77.0%. Comparing base (9a130e9) to head (4d69dac).
Report is 9 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##            main    #282     +/-   ##
=======================================
- Coverage   77.0%   77.0%   -0.1%     
=======================================
  Files        213     213             
  Lines      16512   16512             
=======================================
- Hits       12724   12723      -1     
- Misses      3788    3789      +1     

see 14 files with indirect coverage changes