Iinitial instructions for NixOS prerequisites (#2745)

Co-authored-by: Tillmann <[email protected]>

Author: fcoury

src/content/docs/start/prerequisites.mdx

@@ -119,7 +119,31 @@ sudo apk add \
   </TabItem>
   <TabItem label="NixOS">
 
-TODO: Need to build out NixOS instructions
+Using `nix-shell`:
+
+```
+with import <nixpkgs> { };
+mkShell {
+  buildInputs = [
+    at-spi2-atk
+    atkmm
+    cairo
+    gdk-pixbuf
+    glib
+    gobject-introspection
+    gobject-introspection.dev
+    gtk3
+    harfbuzz
+    librsvg
+    libsoup_3
+    pango
+    webkitgtk_4_1
+    webkitgtk_4_1.dev
+  ];
+
+  PKG_CONFIG_PATH = "${glib.dev}/lib/pkgconfig:${libsoup_3.dev}/lib/pkgconfig:${webkitgtk_4_1.dev}/lib/pkgconfig:${at-spi2-atk.dev}/lib/pkgconfig:${gtk3.dev}/lib/pkgconfig:${gdk-pixbuf.dev}/lib/pkgconfig:${cairo.dev}/lib/pkgconfig:${pango.dev}/lib/pkgconfig:${harfbuzz.dev}/lib/pkgconfig";
+}
+```
 
   </TabItem>
 </Tabs>