[documentation] Update formatting

Author: zombieFox

README.md

@@ -13,10 +13,10 @@ New-tab-page/Start-page for all browsers
 - Saves data to local storage
 - Keyboard shortcuts
 - esc to dismiss most things
-- ctrl+alt+a to add a new bookmark
-- ctrl+alt+m to open menu
-- ctrl+alt+e to toggle edit state
-- ctrl+alt+r random theme if option is turned on in menu > layout > random Accent colour
+-<kbd>ctrl</kbd>+<kbd>alt</kbd>+<kbd>a</kbd> *to add a new bookmark*
+-<kbd>ctrl</kbd>+<kbd>alt</kbd>+<kbd>m</kbd> *to open menu*
+-<kbd>ctrl</kbd>+<kbd>alt</kbd>+<kbd>e</kbd> *to toggle edit state*
+-<kbd>ctrl</kbd>+<kbd>alt</kbd>+<kbd>r</kbd> *random theme if option is turned on in menu > layout > random Accent colour*
 - Responsive design
 - Customise Accent colour!
 - Can be installed on Chrome as an extension