Add variations on start and build scripts for Windows systems

These scripts set an environment variable before invoking
react-app-rewired. The syntax for doing this is different on Windows
systems. Two new scripts are defined to make these actions available to
Windows users.

package.json

@@ -47,7 +47,9 @@
   },
   "scripts": {
     "start": "NODE_OPTIONS=--openssl-legacy-provider react-app-rewired start",
+    "start:win": "set NODE_OPTIONS=--openssl-legacy-provider && react-app-rewired start",
     "build": "NODE_OPTIONS=--openssl-legacy-provider react-app-rewired build",
+    "build:win": "set NODE_OPTIONS=--openssl-legacy-provider && react-app-rewired build",
     "serve-build": "node scripts/serve-build.js",
     "lint": "eslint \"./src/**/*.js\"",
     "lint-fix": "eslint \"./src/**/*.js\" --fix",