Adds new book to index.ngdoc booklist

[jfmercer]

Professional AngularJS is, IME, one of the best books out there on Angular. It would make a nice addition to the booklist.

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[googlebot]

Thanks for your pull request. It looks like this may be your first contribution to a Google open source project. Before we can look at your pull request, you'll need to sign a Contributor License Agreement (CLA).

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[jfmercer]

I signed it!

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CLAs look good, thanks!

[googlebot]

CLAs look good, thanks!