FY21-Q4 Enablement KR: Add 2 maintainers => 50%

Backend Trainees:

• Ian: #7092 (closed)
• Ian: #7093 (closed)
• Aleksei: #7702 (closed)
• Matthias: #6363 (closed)
• Nikola: #6189 (closed)
• Dmitry: #6765 (closed)

Frontend Trainees:

• Zack: #7376 (closed)

DB Trainees:

• Alex: #5437 (closed)