Added Site search similar in function to the Gov design system site. When searching with JS enabled they are offered potential keyword matches in a dropdown. With no JS enabled, when the user searches the form is posted and they are teken to a results page.
# Screenshots
![Screenshot of Search closed screenshot](/images/site-search/01-search-closed-screenshot.jpg)
![Screenshot of Search open screenshot](/images/site-search/02-search-open-screenshot.jpg)
![Screenshot of Search active screenshot](/images/site-search/03-search-active-screenshot.jpg)
![Screenshot of Search no js screenshot](/images/site-search/04-search-no-js-screenshot.jpg)
![Screenshot of Search no js result screenshot](/images/site-search/05-search-no-js-result-screenshot.png)