doc: update hacking

doc/Hacking.md

@@ -4,10 +4,11 @@ Hacking
 Developing UI Widgets
 ---------------------
 
-If you need to create new UI widgets, `utils/wbuilder.lua` is your friend. It
+`utils/wbuilder.lua` is your friend, if you need to create new UI widgets. It
 sets up a minimal environment to bootstrap KOReader's UI framework to avoid
 starting the whole reader. This gives you quick feedback loop while iterating
-through your widget changes.
+through your widget changes. It's also a handy tool for debugging widget
+issues.
 
 To get a taste of how it works, try running this command at the root of
 KOReader's source tree:
@@ -19,5 +20,5 @@ KOReader's source tree:
 It will spawn up an emulator window with a grid and simple timer widget for
 demonstration.
 
-You can add your own `UIManager:show` show call at the end of
-`utils/wbuilder.lua` to test your new widget.
+You can add more `UIManager:show` call at the end of `utils/wbuilder.lua` to
+test your new widgets.