[Feature Request]: Retro: Add stickers and reactions

[rdelcorro]

Description

As a previous user of Trello we were used to comment and add stickers and reactions to the brainstorm phase of retro. It allows other team members to add a lot of value to every item and participate more. You also see the entire team participation visually which is very important

Describe the solution you'd like

Try to follow a similar pattern that trello uses

Describe alternatives you've considered

There is no workaround

[StevenWeathers]

A ticket exists to add comments to brainstorm items #526 so consider this ticket as an ask for Reactions and/or Stickers.