convert the screenshots to jpgs

README.md

@@ -7,9 +7,9 @@ Albums are sorted by the modified time of the last item in them from the latest
 
 <a href='https://play.google.com/store/apps/details?id=com.simplemobiletools.gallery'><img alt='Get it on Google Play' src='https://play.google.com/intl/en_us/badges/images/generic/en_badge_web_generic.png' height=60/></a>
 
-<img alt="App image" src="screenshots/app.png" width="250">
-<img alt="App image" src="screenshots/app_2.png" width="250">
-<img alt="App image" src="screenshots/app_3.png" width="250">
+<img alt="App image" src="screenshots/app.jpg" width="250">
+<img alt="App image" src="screenshots/app_2.jpg" width="250">
+<img alt="App image" src="screenshots/app_3.jpg" width="250">
 
 License
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