chore: explicitly add devDependencies for monorepo peerDependencies (#2808)

packages/medusa-source-shopify/package.json

@@ -44,7 +44,8 @@
     "@babel/runtime": "^7.15.4",
     "client-sessions": "^0.8.0",
     "cross-env": "^7.0.3",
-    "jest": "^26.6.3"
+    "jest": "^26.6.3",
+    "medusa-interfaces": "^1.3.3"
   },
   "gitHead": "cd1f5afa5aa8c0b15ea957008ee19f1d695cbd2e",
   "keywords": [