To search against Wikidata, type "wd" in the search bar, followed by your search terms. Up to three results will be shown. These are indicated by a small Wikidata logo. Each result contains the English label followed by the English description, when available. Selecting an item allows you to preview the URL. Clicking on it or hitting enter after selecting it takes you to the item on wikidata.org. At this point, only English labels and descriptions for items will be searched against. You can contribute to this open source project by getting the source at https://github.com/JeroenDeDauw/WikidataChromeSearch