Add SearchResults Provider

[konapun]

I'm migrating from airline to galaxyline and in the process created a custom provider function for fetching live search results and displaying them in the same manner as airline does:

In this example I'm searching for the text "search term" and vim has found 3 results and I have the second match highlighted.

The SearchResults provider behaves in the following way

• If highlight search results (v:hlsearch) is not active, return nothing
• If hlsearch is active but there are no results for the search, return nothing
• Else, return a results string formatted in the same way as airline, as /search_term [current_result/max_results]