01-margin-and-padding-1: 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/01-margin-and-padding-1/README.md

@@ -7,8 +7,8 @@ For this first exercise, simply edit the `style.css` file so that the divs look
 ### 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.
 
-- Div One and Div Three have 32px between their text and border.
-- Div One has 12px between it and any other element on the page.
-- There is a 48px gap between Div Two and Div Three.
-- Div Three is aligned to the right.
-- Div Three's alignment is achieved using `margin` (and not float, flexbox, etc.).
+- [ ] Div One and Div Three have 32px between their text and border.
+- [ ] Div One has 12px between it and any other element on the page.
+- [ ] There is a 48px gap between Div Two and Div Three.
+- [ ] Div Three is aligned to the right.
+- [ ] Div Three's alignment is achieved using `margin` (and not float, flexbox, etc.).