chore: move @primer/css metadata to package.json

package.json

@@ -1,5 +1,23 @@
 {
-  "private": true,
+  "name": "@primer/css",
+  "version": "11.0.0",
+  "description": "Primer is the CSS framework that powers GitHub's front-end design. primer includes 23 packages that are grouped into 3 core meta-packages for easy install. Each package and meta-package is independently versioned and distributed via npm, so it's easy to include all or part of Primer within your own project.",
+  "homepage": "http://primer.github.io/",
+  "author": "GitHub, Inc.",
+  "license": "MIT",
+  "style": "build/build.css",
+  "sass": "index.scss",
+  "main": "build/index.js",
+  "repository": "https://github.com/primer/css",
+  "bugs": {
+    "url": "https://github.com/primer/css/issues"
+  },
+  "keywords": [
+    "primer",
+    "css",
+    "github",
+    "design-system"
+  ],
   "scripts": {
     "build": "scripts/build",
     "prepare": "npm run build",