Apply NYU's " + ^ " icon styling for "Add new item above this one" in Lessons

In Lessons, to provide clarity re: the inline "" icon that appears to the right of individual items, update the icon to instead use a combo FA icon of a "" (fa-plus) with a small upward arrow in the upper-right corner (fa-arrow-up):

This differentiation helps to visually inform the user of the differences between the 3 different "Add content" options in Lessons:

• "Add Content" tool tab button - adds content at the bottom of the page
• "+" button at the bottom of columns / sections - adds content at the bottom of that section
• Inline " +^ " button - adds content directly above the current item.