Add Electron windowOptions

[jbreckmckye]

You can now pass options to the electron BrowserWindow by adding a windowOptions object to your config, e.g.

const auth = new ElectronAuth0Login({
    auth0Audience: 'https://api.mydomain.com',
    auth0ClientId: 'abc123ghiMyApp',
    auth0Domain: 'my-domain.eu.auth0.com',
    auth0Scopes: 'given_name profile',
    windowOptions: {
        width: 1024,
        height: 640,
    }
});

These options will be merged into the default options, which are

{
    width: 800,
    height: 600,
    alwaysOnTop: true,
    title: 'Log in',
    backgroundColor: '#202020'
};