Update raycast-gemini extension

[ViGeng]

Description

• Add new model options:
  • gemini-2.0-flash-exp
  • gemini-1.5-flash-8b
• Refine Summarize prompt

Screencast

Checklist

• I read the extension guidelines
• I read the documentation about publishing
• I ran npm run build and tested this distribution build in Raycast
• I checked that files in the assets folder are used by the extension itself
• I checked that assets used by the README are placed outside of the metadata folder

[raycastbot]

Thank you for your contribution! 🎉

🔔 @EvanZhouDev @ridemountainpig you might want to have a look.

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