Make all Embed fields except for 'kind' optional
Make all Embed fields except for 'kind' optional

Embeds can return any combination - or a lack of - fields, so they need
to all be optional, except for 'type'.

eLunate/serenity,Roughsketch/serenity,zeyla/serenity,Lakelezz/serenity,acdenisSK/serenity,zeyla/serenity.rs,Flat/serenity