fix: README search results image format

Author: NumBit

README.md

@@ -28,7 +28,7 @@ If you plan to run this in the cloud, ensure your environment supports persisten
 
 ## Screenshots
 
-![Search results](https://raw.githubusercontent.com/Kentico/xperience-by-kentico-lucene/main/images/dancing-goat-search-results-page.jpg)
+![Search results](https://raw.githubusercontent.com/Kentico/xperience-by-kentico-lucene/main/images/dancing-goat-search-results-page.png)
 
 ![Index listing](https://raw.githubusercontent.com/Kentico/xperience-by-kentico-lucene/main/images/xperience-administration-search-index-list.jpg)