fix typo in extend-info and add support object params

[kwolfy]

Summarize your changes:
fix typo in extend plist
added object params support for the "extend-info"

packager({
  ...
  'extend-info': {
     ElectronTeamId: 'RJ883jd299'
   }
});

Are your changes appropriately documented?
no, My English is not enough for writing docs

Do your changes have sufficient test coverage?
yes

Does the testsuite pass successfully on your local machine?
yes

[malept]

@kwolfy I've updated the docs based on your new feature. Let me know if it's accurate or it needs to be clarified.

[kwolfy]

@malept Thank you, The doc is right

[malept]

Thanks!