[firefox] add 'vici' executable in nix devShell

[teto]

Extension name

firefox

Description

Installing extensions via nix doesn't work that often so I've proceeded to install some imperatively, via npm install + npm run build.

Some of those failed because of vici being unavailable. Seems like it is provided by https://www.npmjs.com/package/@vicinae/api so it would be nice to have https://www.npmjs.com/package/@vicinae/api provided by the nix devShell

vicinae-extensions/extensions/firefox 
➜ npm run build

> build
> vici build

sh: ligne 1: vici: commande introuvable

Steps to reproduce

No response

Vicinae version

v0.20.7

[github-actions]

cc @knoopx