Search bar for Merged Pull Requests page.

It would be better to have a search bar for merged pull requests page.

Since, active pull requests page doesn't contain more than 1 page pull requests generally, it is not necessary to have a search bar for a pull request. But, for merged pull requests page, there are many merged pull requests and that is getting bigger day-by-day. When I want to look at a merged pull request with a keyword that is only thing that I remember about the related pull request, I can not use any search function, yet. I have to go through all pages manually.