add tests badge and overview video

README.md

@@ -1,9 +1,13 @@
+[![Tests](https://github.com/umn-cla/smartycards/actions/workflows/test.yml/badge.svg)](https://github.com/umn-cla/smartycards/actions/workflows/test.yml)
+
 # SmartyCards
 
 > Flashcards, but smarter
 
 ## Introduction
 
+<iframe width="560" height="315" src="https://www.youtube-nocookie.com/embed/2KR-T_Pt3cI?si=1Lh35s-vMk7E_hX9" title="YouTube video player" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture; web-share" referrerpolicy="strict-origin-when-cross-origin" allowfullscreen></iframe>
+
 SmartyCards is a free, collaborative platform for studying with digital flashcards, quizzes, and games. Any student, faculty, or staff at any University of Minesota campus can use SmartyCards.
 
 - Sign in: [smartycards.cla.umn.edu](https://smartycards.cla.umn.edu)