docs/installation: add standalone flake example

docs/manual/installation/custom-configuration.md

@@ -1,8 +1,9 @@
 # Standalone Installation {#ch-standalone-installation}
 
-It is possible to install **nvf** without depending on NixOS or home-manager as the parent
-module system, using the `neovimConfiguration` function exposed by **nvf** extended library.
-It takes in the configuration as a module, and returns an attribute set as a result.
+It is possible to install nvf without depending on NixOS or Home-Manager as the
+parent module system, using the `neovimConfiguration` function exposed in the
+extended library. This function will take `modules` and `extraSpecialArgs` as
+arguments, and return the following schema as a result.
 
 ```nix
 {
@@ -13,6 +14,53 @@ It takes in the configuration as a module, and returns an attribute set as a res
 }
 ```
 
+An example flake that exposes your custom Neovim configuration might look like
+
+```nix
+{
+  inputs = {
+    nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
+    nvf.url = "github:notashelf/nvf";
+  };
+
+  outputs = {
+    self,
+    nixpkgs,
+    ...
+  } @ inputs: {
+    packages."x86_64-linux" = let
+        neovimConfigured = (inputs.nvf.lib.neovimConfiguration {
+          inherit (nixpkgs.legacyPackages."x86_64-linux") pkgs;
+          modules = [{
+              config.vim = {
+                # Enable custom theming options
+                theme.enable = true;
+
+                # Enable Treesitter
+                tree-sitter.enable = true;
+
+                # Other options will go here. Refer to the config
+                # reference in Appendix B of the nvf manual.
+                # ...
+              };
+          }];
+        });
+    in {
+      # Set the default package to the wrapped instance of Neovim.
+      # This will allow running your Neovim configuration with
+      # `nix run` and in addition, sharing your configuration with
+      # other users in case your repository is public.
+      default = neovimConfigured.neovim;
+    };
+  };
+}
+```
+
+<!-- TODO: mention the built-in flake template here when it is added -->
+
+The next two chapters will detail specific usage of standalone nvf
+configurations on NixOS and Home-Manager.
+
 ```{=include=} chapters
 standalone/nixos.md
 standalone/home-manager.md