added package.json

add package.json so `yarn` can install it (currently fails with "Couldn't find manifest" due to a [bug](yarnpkg/yarn#1747))

package.json

@@ -0,0 +1,19 @@
+{
+  "name": "@polymerelements/font-roboto",
+  "version": "1.0.1",
+  "description": "An HTML import for Roboto",
+  "authors": [
+    "The Polymer Authors"
+  ],
+  "keywords": [
+    "font",
+    "roboto"
+  ],
+  "repository": {
+    "type": "git",
+    "url": "git://github.com/PolymerElements/font-roboto.git"
+  },
+  "main": "roboto.html",
+  "license": "http://polymer.github.io/LICENSE.txt",
+  "homepage": "https://github.com/PolymerElements/font-roboto/"
+}