Allow to select mailbox when creating an alias from the browser extension

[MarkWieczorek]

The browser extension for creating new aliases is great! There is only one aspect that I wish was a little better:

When creating an alias, it uses the default mailbox of your account. It would be really helpful to me if you could easily select the mailbox to use when creating an alias from the browser extension. Furthermore, if it were possible, it would be great if you could set a different default mailbox to use on different computers (i.e., work vs. personal).