01-button-hover: Add checkboxes to the README

Add checkboxes to the README to make the progress tracking a better experience.

Author: gs-101

advanced-html-css/animation/01-button-hover/README.md

@@ -7,6 +7,6 @@ Use a transition to scale the button when you hover your mouse over it.
 ![outcome](./desired-outcome.gif)
 
 ### Self Check
-- Does the button grow when you hover it?
-- Do other properties of the button remain unchanged?
-- Does the `:hover` pseudo-class trigger the transition?
+- [ ] Does the button grow when you hover it?
+- [ ] Do other properties of the button remain unchanged?
+- [ ] Does the `:hover` pseudo-class trigger the transition?