01-margin-and-padding-2: Add checkboxes to the README

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

Author: gs-101

foundations/block-and-inline/02-margin-and-padding-2/README.md

@@ -8,11 +8,11 @@ This one is a little nicer looking, and a little closer to something you might s
 ### Self Check
 Use this section to check your work. On _these_ projects, your goal isn't to attain 100% pixel perfection, but to use the tools you've learned to get relatively close to the desired output.
 
-- There is 8px between the edge of the card and its content (the blue sections).
-- There is an 8px gap between each of the blue sections inside the card.
-- The title of the card uses a 16px font.
-- There are 8px between the title text and the edge of the title section.
-- The content section has 16px space on the top and bottom, and 8px on either side.
-- Everything inside the `.button-container` section is centered, and there is 8px padding.
-- The Big Button is centered on its own line.
-- The Big Button has 24px space on the sides, and 8px on top and bottom.
+- [ ] There is 8px between the edge of the card and its content (the blue sections).
+- [ ] There is an 8px gap between each of the blue sections inside the card.
+- [ ] The title of the card uses a 16px font.
+- [ ] There are 8px between the title text and the edge of the title section.
+- [ ] The content section has 16px space on the top and bottom, and 8px on either side.
+- [ ] Everything inside the `.button-container` section is centered, and there is 8px padding.
+- [ ] The Big Button is centered on its own line.
+- [ ] The Big Button has 24px space on the sides, and 8px on top and bottom.