Support searching via URL

[nex3]

I'd like to set up a Chrome search handler to search the Dart core library APIs, but currently this isn't possible because there's no way to construct a URL for a search query. It would be great to support something like this.

One possibility for an easy implementation that avoids the need for a search results page:

• When a DartDoc page first loads, check for the presence of a query parameter named "search".
• If such a parameter exists, find the first autocomplete result that would be chosen if the search string were typed in the search bar.
• If there is such a result, navigate to its page.

[sethladd]

Sounds great!