Add open-in-github-copilot extension

[dfosco]

Description

Adds extension to enter and open prompt in GitHub Copilot Web from Raycast:

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]

Congratulations on your new Raycast extension! 🚀

You can expect an initial review within five business days.

Once the PR is approved and merged, the extension will be available on our Store.

[ViGeng]

Interesting, never explored Github Copilot!
Alternatively, another "lightweight" idea should be just using a Quicklink:

https://github.com/copilot?prompt={argument name="Argument"}
https://github.com/copilot?prompt={selection}

Just inspired by this PR, share some thoughts :-)