Add emoji picker to cast modal

[willyogo]

As a user, i want to be able to include emojis in my casts.

AC:

1. An emoji picker is added to the cast modal
2. Users can scroll, search, and select any emoji
3. When a user clicks an emoji, it's added to cast either where the cursor last was or at the end of the cast

[sktbrd]

After the latest changes on the cast modal are merged I can make this one , to avoid conflicts with a suck important file