fix(nixfmt): update repo link and description (#505)

* feat(formatters): add nixfmt-rfc-style

docs: add nixfmt-rfc-style to readme and conform.txt

* feat: replace nixfmt with nixfmt-rfc-style

* doc: ensure description has period at the end

---------

Co-authored-by: Steven Arcangeli <[email protected]>

README.md

@@ -283,7 +283,7 @@ You can view this list in vim with `:help conform-formatters`
 - [mix](https://hexdocs.pm/mix/main/Mix.Tasks.Format.html) - Format Elixir files using the mix format command.
 - [nickel](https://nickel-lang.org/) - Code formatter for the Nickel programming language.
 - [nimpretty](https://github.com/nim-lang/nim) - nimpretty is a Nim source code beautifier that follows the official style guide.
-- [nixfmt](https://github.com/serokell/nixfmt) - nixfmt is a formatter for Nix code, intended to apply a uniform style.
+- [nixfmt](https://github.com/NixOS/nixfmt) - The official (but not yet stable) formatter for Nix code.
 - [nixpkgs_fmt](https://github.com/nix-community/nixpkgs-fmt) - nixpkgs-fmt is a Nix code formatter for nixpkgs.
 - [npm-groovy-lint](https://github.com/nvuillam/npm-groovy-lint) - Lint, format and auto-fix your Groovy / Jenkinsfile / Gradle files using command line.
 - [ocamlformat](https://github.com/ocaml-ppx/ocamlformat) - Auto-formatter for OCaml code.

doc/conform.txt

@@ -394,8 +394,7 @@ FORMATTERS                                                    *conform-formatter
 `nickel` - Code formatter for the Nickel programming language.
 `nimpretty` - nimpretty is a Nim source code beautifier that follows the
             official style guide.
-`nixfmt` - nixfmt is a formatter for Nix code, intended to apply a uniform
-         style.
+`nixfmt` - The official (but not yet stable) formatter for Nix code.
 `nixpkgs_fmt` - nixpkgs-fmt is a Nix code formatter for nixpkgs.
 `npm-groovy-lint` - Lint, format and auto-fix your Groovy / Jenkinsfile / Gradle
                   files using command line.

lua/conform/formatters/nixfmt.lua

@@ -1,8 +1,8 @@
 ---@type conform.FileFormatterConfig
 return {
   meta = {
-    url = "https://github.com/serokell/nixfmt",
-    description = "nixfmt is a formatter for Nix code, intended to apply a uniform style.",
+    url = "https://github.com/NixOS/nixfmt",
+    description = "The official (but not yet stable) formatter for Nix code.",
   },
   command = "nixfmt",
 }