Add @11ty/eleventy package to dev shell

pkgs/11ty-eleventy.nix

@@ -0,0 +1,15 @@
+# We'll pass in the pkgs and `src`
+{ pkgs, src }:
+pkgs.buildNpmPackage {
+  # Package name
+  pname = "eleventy";
+  version = (builtins.readFile ./11ty-eleventy.version) + "main";
+  src = src;
+  npmDepsHash = builtins.readFile ./11ty-eleventy.sha256;
+  dontNpmBuild = true;
+  meta = with pkgs.lib; {
+    description = "A simpler static site generator";
+    homepage = "https://www.11ty.dev/";
+    license = licenses.mit;
+  };
+}

pkgs/11ty-eleventy.sha256

@@ -0,0 +1 @@
+sha256-LGdCM1gjt3hRn7BiIlbA4e2HOiQ6e/qkAtWp0Qwn+PE=

pkgs/11ty-eleventy.version

@@ -0,0 +1 @@
+3.1.2-beta.2