feat(AvatarGroup): new component (#71)

Co-authored-by: Romain Hamel <romain@boilr.io>

src/theme/index.ts

@@ -1,6 +1,7 @@
 export { default as accordion } from './accordion'
 export { default as alert } from './alert'
 export { default as avatar } from './avatar'
+export { default as avatarGroup } from './avatar-group'
 export { default as badge } from './badge'
 export { default as breadcrumb } from './breadcrumb'
 export { default as button } from './button'