ngrok installation requires --unsafe-perm=true in the install script, which is unusual and should be avoided for the main installation instructions.

It is already an optional feature only triggered by --ngrok, so it is probably better to make it an optional npm dependency and ask people to install it separately using npm install -g ngrok --unsafe-perm=true if needed.

• move ngrok to optionalDependencies
• load only if needed (--ngrok argument specified ) as illustrated here
• if not installed, give error message explaining how to install it