Final capsule types

[DavidSchinazi]

Please switch to one-byte capsule types (values 0-63).

You can register them by filing a request here and @LPardue or I can approve them.

Current available values are visible here. Make sure to request values as provisional in this request, and mention in the IANA considerations of the doc that they will be made permanent when the RFC is published.

[martinthomson]

You can select a value here if you want a random* draw that is verifiably not grease or already taken.