Allow Design Annotations to be awarded emoji

Problem to solve

We would like users to be able to award emoji to Annotations on designs.

Further details

The backend GraphQL work to enable this is captured in these issues:

• https://gitlab.com/gitlab-org/gitlab-ce/issues/62826
• https://gitlab.com/gitlab-org/gitlab-ce/issues/63797

This issue, therefore, represents the design and front-end work in order to

• allow the user to choose an emoji to give to ("award") an Annotation
• display the emojis awarded to Annotations