feat(emacs): use emacsclient to emacs by default

[sei40kr]

Use emacsclient to open Emacs by default.

NixOS

Emacs daemon is provided by services.emacs. https://search.nixos.org/options?channel=unstable&from=0&size=50&sort=relevance&type=packages&query=services.emacs https://github.com/NixOS/nixpkgs/blob/master/nixos/modules/services/editors/emacs.nix

Also need to remove the desktop entry that opens Emacs without emacsclient. https://github.com/NixOS/nixpkgs/blob/master/nixos/modules/services/editors/emacs.xml#L340-L344

Darwin

Emacs daemon is provided by services.emacs. https://daiderd.com/nix-darwin/manual/index.html