Bug in web-ext using a package.json configfile

[merrx]

Bug in web-ext using a package.json configfile in the same directory.
This line causes the issue and errors out with the message "channel" has not defined a type
"sign": {
"channel": "unlisted"
}
This is caused by missing " type: 'string' " on line 617
https://github.com/mozilla/web-ext/blob/ca73b70611971cdde22467abc5a7bdd530fa69f8/src/program.js