chore: include screenshot of popup

Unlike weather widget I only have the current weather in place here.
I'm okay with the default font so I have not created another screenshot.

Signed-off-by: André Jaenisch <andre.jaenisch@posteo.de>

weather-api-widget/README.md

@@ -1,5 +1,7 @@
 # WeatherAPI widget
 
+![Current Weather popup](./popup.png)
+
 The widget consists of one section:
 - current weather, including humidity, wind speed, UV index
 
@@ -30,7 +32,7 @@ use the folder name in widget's config. There should be 18 icons, preferably
 128x128 minimum. Icons should also respect the naming convention, please check
 widget's source.
 
-### Examples:
+### Examples
 
 #### Custom font, icons