chore: add lesson_09 additional video (#280)

Signed-off-by: Anthony D. Mays <[email protected]>

Author: anthonydmays

lesson_09/README.md

@@ -6,6 +6,7 @@ Please review the following resources before lecture:
 
 * [Learn Java Primitive Data Types in 5 Minutes (Video)](https://www.youtube.com/watch?v=cgp5ulbsdJ0)
 * [Java Classes & Objects (Video)](https://www.youtube.com/watch?v=IUqKuGNasdM)
+* [TypeScript Tutorial #12 - Classes (Video)](https://www.youtube.com/watch?v=OsFwOzr3_sE)
 
 ## Homework