Add explicit node types dependency

Author: JordonPhillips

smithy-typescript-ssdk-libs/server-apigateway/package.json

@@ -29,6 +29,7 @@
   },
   "devDependencies": {
     "@types/jest": "^26.0.4",
+    "@types/node": "^12.7.5",
     "downlevel-dts": "^0.7.0",
     "jest": "^26.1.0",
     "typescript": "~4.1.2"

smithy-typescript-ssdk-libs/server-common/package.json

@@ -29,6 +29,7 @@
   },
   "devDependencies": {
     "@types/jest": "^26.0.20",
+    "@types/node": "^12.7.5",
     "downlevel-dts": "^0.7.0",
     "jest": "^26.6.3",
     "ts-jest": "^26.5.2",