Fix incorrect extension for custom screenshot file name (fixes #337)

src/main/java/com/replaymod/extras/advancedscreenshots/GuiCreateScreenshot.java

@@ -95,6 +95,11 @@ public class GuiCreateScreenshot extends GuiRenderSettings implements Loadable {
         }
     }
 
+    @Override
+    public void load(RenderSettings settings) {
+        super.load(settings.withEncodingPreset(RenderSettings.EncodingPreset.PNG));
+    }
+
     @Override
     protected Path getSettingsPath() {
         return getMinecraft().runDirectory.toPath().resolve("config/replaymod-screenshotsettings.json");