[nix] Redo and restructure the entire config

Thanks @KaitlynEthylia :)

nix/home/nvim.nix

@@ -0,0 +1,38 @@
+{ self, pkgs, ... }:
+
+{
+  programs.neovim = {
+    enable = true;
+    package = pkgs.neovim-unwrapped;
+
+    extraConfig = ''source ~/.dotfiles/nvim/init.vim"source ${self}/nvim/init.vim'';
+
+    coc = {
+      enable = true;
+
+      settings = {
+        languageserver = {
+          nix = {
+            command = "nil";
+            filetypes = [ "nix" ];
+            rootPatterns = [ "flake.nix" ];
+            "settings.nil" = {
+              "formatting.command" = [ "nixpkgs-fmt" ];
+            };
+          };
+          "go.goPlsOptions" = {
+            completion = true;
+            completeUnimported = true;
+          };
+          rescript = {
+            enable = true;
+            command = "rescript-language-server";
+            args = [ "--node-ipc" ];
+            filetypes = [ "rescript" ];
+            rootPatterns = [ "rescript.json" "bsconfig.json" ];
+          };
+        };
+      };
+    };
+  };
+}