Move @types/multer to dependencies (#401)

Co-authored-by: David Garner <dgarner@qmetric.co.uk>

package.json

@@ -31,6 +31,7 @@
   "author": "Carmine DiMascio <cdimascio@gmail.com>",
   "license": "MIT",
   "dependencies": {
+    "@types/multer": "^1.4.4",
     "ajv": "^6.12.5",
     "content-type": "^1.0.4",
     "js-yaml": "^3.14.0",
@@ -49,7 +50,6 @@
     "@types/express": "^4.17.8",
     "@types/mocha": "^8.0.3",
     "@types/morgan": "^1.9.1",
-    "@types/multer": "^1.4.4",
     "@types/node": "^14.6.4",
     "@types/supertest": "^2.0.10",
     "body-parser": "^1.19.0",