Read description from plugin's package json

Summary: Added "description" field to PluginDetails interface and read it from package.json

Reviewed By: passy

Differential Revision: D21927391

fbshipit-source-id: 0513637d3afa3d8be8e2bc8ee87cc1d77c5e2250

desktop/plugin-lib/src/PluginDetails.ts

@@ -17,7 +17,8 @@ export default interface PluginDetails {
   id: string;
   gatekeeper?: string;
   icon?: string;
-  title?: string;
+  title: string;
+  description?: string;
   category?: string;
   bugs?: {
     email?: string;