Write Release Notes for V1.2.0

[juliavisserinbibo]

The release notes should include the changes done in the following issues:

Shift

• Improvement: https://github.com/Inbibo/shift/issues/966
• Improvement: https://github.com/Inbibo/shift/issues/797
• Added: https://github.com/Inbibo/shift/issues/918
• Added: https://github.com/Inbibo/shift/issues/811
• Added: https://github.com/Inbibo/shift/issues/1258

DCC Integration

• Added: https://github.com/Inbibo/Shift_USD/issues/233
• Added: https://github.com/Inbibo/Shift_USD/issues/227
• Fix: https://github.com/Inbibo/Shift_USD/issues/215