chore(README): format nix codeblock and paragraph better

Author: CompeyDev

README.md

@@ -45,8 +45,8 @@ cargo run --release --no-default-features -- --help
 
 ### with nix
 
-the nix flake exports a package with an overridable `features` attribute. `default.nix` exports two variants using this, 
-`ssh-portfolio` and `ssh-portfolio-blog`.
+the nix flake exports a package with an overridable `features` attribute. `default.nix` 
+exports two variants using this, `ssh-portfolio` and `ssh-portfolio-blog`.
 
 ```sh
 nix build --file . ssh-portflio      # without blog
@@ -61,8 +61,9 @@ or with your own set of features to build for:
 ```nix
 # assuming this is in `custom.nix` in the same directory as `flake.nix`:
 { pkgs ? import <nixpkgs> { } }:
-{
-  ssh-portfolio-custom = (builtins.getFlake (builtins.toString ./.)).packages.${pkgs.system}.ssh-portfolio.override { features = [ ... ]; };
+rec {
+  ssh-portfolio = (builtins.getFlake (builtins.toString ./.)).packages.${pkgs.system}.ssh-portfolio;
+  ssh-portfolio-custom = ssh-portfolio.override { features = [ ... ]; };
 }
 ```