Nix add man (#1148)

* update(nix): add manpage to `man` output

* fmt(nix): nixpkgs-fmt

flake.nix

@@ -19,7 +19,8 @@
       "i686-linux"
       "x86_64-darwin"
       "x86_64-linux"
-    ] (system:
+    ]
+      (system:
         let
           overlays = [ (import rust-overlay) ];
 
@@ -50,6 +51,9 @@
           ];
 
           nativeBuildInputs = [
+            # generates manpages
+            pkgs.mandown
+
             pkgs.installShellFiles
             pkgs.copyDesktopItems
 
@@ -61,13 +65,12 @@
             pkgs.cargo-make
             pkgs.rust-analyzer
             pkgs.nixpkgs-fmt
-          # generates manpages
-          pkgs.mandown
             # optimizes wasm binaries
             pkgs.binaryen
           ];
 
-      in rec {
+        in
+        rec {
 
           packages.zellij =
             (pkgs.makeRustPlatform { inherit cargo rustc; }).buildRustPackage {
@@ -78,6 +81,8 @@
               '';
 
               postInstall = ''
+                mandown ./docs/MANPAGE.md > ./zellij.1
+                installManPage ./zellij.1
 
                 # explicit behavior
                 $out/bin/zellij setup --generate-completion bash > ./completions.bash