Changes to get vanilla example working on Windows

[sacah]

In the dev.js script it calls
nodemon(-x 'NGROK_URL=${url} PORT=${port} node' ./backend/server.js);

I imported 'const { exec } = require('child_process');'
Then changed the above line to
exec('SET NGROK_URL='+ url);
nodemon(-x 'node' ./backend/server.js);

Also changed the package.js from export to set.