feat(fastfetch): support product-local renderers

[aethctl]

What changed

Translation layer required to display icat png's on fastfetches like the one found here https://github.com/Sipper1236/inspo-fastfetch

Area

How it was tested

Describe how you verified this on a running system, not only that it parses.

Checklist

• One logical change, with a clear [area] scope: summary commit subject.
• Matching CHANGELOG.md updated in the area I touched.
• The git hooks pass locally; I did not use --no-verify.
• Lua parses (luac -p), shell scripts pass bash -n, and QML passes
  qmllint where applicable.
• No duplicated config, no dead code, no commented-out code, no em-dash.
• Docs updated if behavior or layout changed.

[neur0map]

Thanks @aethctl, merged into unstable-dev with you as the author. I kept the old notes at the top of the script about why it uses exec, and added a line about the renderer hook. It goes out with the next release.