Cleanup: add blank lines for canonical markdown

My markdown formatter in VS Code adds these when I press Command-S.

README.md

@@ -423,6 +423,7 @@ nix-shell -p lazygit
 # or with flakes enabled
 nix run nixpkgs#lazygit
 ```
+
 Or you can add lazygit to your `configuration.nix` using the `environment.systemPackages` option.
 More details can be found via NixOS search [page](https://search.nixos.org/).
 
@@ -431,6 +432,7 @@ More details can be found via NixOS search [page](https://search.nixos.org/).
 This repository includes a nix flake that provides the latest development version and additional development tools:
 
 **Run lazygit directly from the repository:**
+
 ```sh
 nix run github:jesseduffield/lazygit
 # or from a local clone
@@ -438,6 +440,7 @@ nix run .
 ```
 
 **Build lazygit from source:**
+
 ```sh
 nix build github:jesseduffield/lazygit
 # or from a local clone
@@ -446,6 +449,7 @@ nix build .
 
 **Development environment:**
 For contributors, the flake provides a development shell with Go toolchain, development tools, and dependencies:
+
 ```sh
 nix develop github:jesseduffield/lazygit
 # or from a local clone
@@ -453,12 +457,14 @@ nix develop
 ```
 
 The development shell includes:
+
 - Go toolchain
 - git and make
 - Proper environment variables for development
 
 **Using in other flakes:**
 The flake also provides an overlay for easy integration into other flake-based projects:
+
 ```nix
 {
   inputs.lazygit.url = "github:jesseduffield/lazygit";