Update gitignore

[Janaka-Steph]

Review checklist

Don't worry about satisfying all items, it's fine to open a (draft) PR.

• [ ] chapter content
  • [ ] only one top-level # h1-Title
  • [ ] summary (e.g. table or TL;DR overview), no need for an explicit ## Summary/Introduction title or equivalent
  • [ ] main content focus: recent developments in open source AI
  • general context/background (brief)
  • current pros/cons
  • in-depth insights (not yet widely known)
  • [ ] likely ## Future developments
  • [ ] end with {{ comments }}
• [ ] appropriate citations
  • [ ] BibTeX references
  • [ ] Glossary terms
  • [ ] cross-references (figures/chapters)
  • [ ] (if new-chapter.md), add _toc.yml entry & index.md table row
  • [ ] If CI URL checks have false-positives, append to _config.yml:sphinx.config.linkcheck*
• [ ] images & data not committed to this repo (e.g. use https://github.com/premAI-io/static.premai.io instead)