Add nix-flake-templates extension

[lex-unix]

Description

Copy/paste flake templates from the-nix-way/dev-templates.

Special thanks to the gitignore extension which served as a blueprint for creating this extension.

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! 🚀

Due to our current reduced availability, the initial review may take up to 10-15 business days 🎄

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