Update placeholder for Key Investigators list format

Added a note to emphasize list format for Key Investigators.

Author: sjh26

.github/ISSUE_TEMPLATE/project.yml

@@ -53,6 +53,7 @@ body:
       `- Firstname Lastname (Affiliation, Country)`
       **IT MUST BE IN LIST FORMAT**
     placeholder: |
+      - LIST FORMAT!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
       - FirstName1 LastName1 (Affiliation, Country)
       - FirstName2 LastName2 (Affiliation, Country)
       - FirstName3 LastName3 (Affiliation, Country)