improve software-specific pages in software overview

[boegel]

• based https://www.eessi.io/api_data/data/eessi_api_metadata_software.json
• covers installations in both EESSI 2023.06 and 2025.06
• also exposes GPU info

preview available via:

• https://boegel.github.io/EESSI-docs/available_software/ (basically untouched, except for using relative links and making them open in a new tab);
• example software-specific pages:
  • https://boegel.github.io/EESSI-docs/available_software/detail/GROMACS (with GPU labels);
  • https://boegel.github.io/EESSI-docs/available_software/detail/SciPy-bundle (small number of extensions);
  • https://boegel.github.io/EESSI-docs/available_software/detail/R-bundle-CRAN (huge number of extensions);

[ocaisa]

LGTM, based on the end result