Show related search terms to support quick re-expression.

In a recent user study, we found that users use short search terms on pub.dev that summarizes the feature they need. When it is not clear what keyword to search, users start with a query that is relevant to the topic and get hints for query refinement from the search results. When it’s difficult to express, some users rely on the community to find the correct term.

We can provide additional features, like showing related search terms, to support quick re-expression. (Alternatively, we can support "tags" for packages and show relevant tags.)