Allow configuring Electron via CLI

# Description - Switches unix-opts to Atlas fork - Updates cl-electron to a version supporting passing additional args - Adds --electron-opts to Nyxt's CLI # Checklist: - [x] Git branch state is mergable. - [x] Changelog is up to date (via a separate commit). - [x] New dependencies are accounted for. - [x] Documentation is up to date. - [x] Compilation and tests (`(asdf:test-system :nyxt/<renderer>)`) - No new compilation warnings. - Tests are sufficient.