Add `prettier`

package.json

@@ -133,6 +133,7 @@
     "node-sass-import-once": "^1.2.0",
     "nsp": "^3.2.1",
     "nyc": "^11.4.1",
+    "prettier": "1.12.0",
     "qs": "^6.5.1",
     "react-docgen-typescript": "^1.2.6",
     "react-styleguidist": "^7.0.1",

yarn.lock

@@ -6893,6 +6893,10 @@ preserve@^0.2.0:
   version "0.2.0"
   resolved "https://registry.yarnpkg.com/preserve/-/preserve-0.2.0.tgz#815ed1f6ebc65926f865b310c0713bcb3315ce4b"
 
+prettier@1.12.0:
+  version "1.12.0"
+  resolved "https://registry.yarnpkg.com/prettier/-/prettier-1.12.0.tgz#d26fc5894b9230de97629b39cae225b503724ce8"
+
 pretty-bytes@^1.0.2:
   version "1.0.4"
   resolved "https://registry.yarnpkg.com/pretty-bytes/-/pretty-bytes-1.0.4.tgz#0a22e8210609ad35542f8c8d5d2159aff0751c84"