chore: added a dev command (#42)

* chore: added a dev command

* changed yarn to npm

package.json

@@ -14,11 +14,12 @@
   ],
   "scripts": {
     "clean": "./node_modules/.bin/rimraf dist",
-    "build": "yarn run clean && tsc -p tsconfig.json",
+    "build": "npm run clean && tsc -p tsconfig.json",
     "watch": "tsc --watch",
     "test": "jest",
     "seed": "medusa seed -f ./data/seed.json",
-    "start": "yarn build && medusa start",
+    "start": "npm run build && medusa start",
+    "dev": "npm run build && medusa develop",
     "build:admin": "medusa-admin build"
   },
   "dependencies": {