Add @types/node to typescript boilerplate

Parcel uses process.env to expose environment variables. Since process.env is a
Node concept and this boilerplate is for TypeScript projects, we need
@types/node to support these Node types.

boilerplate/typescript/package.json

@@ -7,6 +7,7 @@
     "dev": "npx parcel src/index.html & npx tsc --watch --noEmit"
   },
   "devDependencies": {
+    "@types/node": "^13.9.3",
     "parcel-bundler": "^1.12.4",
     "tailwindcss": "^1.2.0",
     "typescript": "^3.8.3"

boilerplate/typescript/yarn.lock

@@ -880,6 +880,11 @@
     "@types/react" "*"
     hoist-non-react-statics "^3.3.0"
 
+"@types/node@^13.9.3":
+  version "13.9.3"
+  resolved "https://registry.yarnpkg.com/@types/node/-/node-13.9.3.tgz#6356df2647de9eac569f9a52eda3480fa9e70b4d"
+  integrity sha512-01s+ac4qerwd6RHD+mVbOEsraDHSgUaefQlEdBbUolnQFjKwCr7luvAlEwW1RFojh67u0z4OUTjPn9LEl4zIkA==
+
 "@types/prop-types@*":
   version "15.7.3"
   resolved "https://registry.yarnpkg.com/@types/prop-types/-/prop-types-15.7.3.tgz#2ab0d5da2e5815f94b0b9d4b95d1e5f243ab2ca7"