Add package quality metrics to Pub PM

[DartBot]

Originally opened as dart-lang/sdk#23269

This issue was originally filed by gabe9693...@gmail.com

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Pub Package Manager currently does not appear to provide any quality info about the packages. When browsing through packages it can be hard to assess package quality. I am suggesting adding user ratings to pub to enable package quality to be assessed. NPM made the mistake of not including this, and now there are third party tools such as this: http://npmsearch.com/ to enhance the NPM browsing experience.

Both user input and other metrics could be used to assess package quality (as in npmsearch.com). There are several ways this could be done, but anything would almost certainly be better than nothing.

Thanks!
:b

[DartBot]

<img src="https://avatars.githubusercontent.com/u/1343914?v=3" align="left" width="48" height="48"hspace="10"> Comment by sgjesse

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Added Area-PubSite, Triaged labels.