Disable opening the browser when in development mode

[severo]

fixes #173 by disabling the automatic opening of a browser tab when the cli restarts.

It means that the workflow in dev would be:

• run npm run dev
• click the URL shown in the console logs (by default http://localhost:2048) to open in a browser
• do some changes in the code -> the new app will be rebuild automatically and the CLI will be restarted too, but the opened tab will still show the outdated version
• manually update the browser tab.

A follow-up could be to set up browser-sync (I could not make it work easily) or another tool to open and reload a browser tab automatically.

[severo]

merging for now, but interested in your feedback @platypii: do you want me to try to get live reload or hot reload, or is it OK now?