update readme; add helper yarn commands

package.json

@@ -1,5 +1,11 @@
 {
   "dependencies": {
     "react-router-dom": "^5.0.1"
+  },
+
+  "scripts": {
+    "dev-db": "docker run --name gangstadb -d -p 5432:5432 -e POSTGRES_PASSWORD=docker -e POSTGRES_DB=roraccounting_development roraccounting",
+    "server": "PORT=3001 bundle exec rails s",
+    "client": "PORT=3000 yarn --cwd client start"
   }
 }