Support Option<T: DesseStatic + DesseSize>

[jrmuizel]

This would be pretty handy.

[djg]

I've been trying to implement this and I'm currently stuck on rust-lang/rust#60551

[devashishdxt]

We wont be able to do this without proper support for const generics. Until then, we can figure out a way to implement DesseDynamic trait for Option<T> which will enable de/serialization of Option<T>.

I haven't pushed DesseDynamic trait in master branch as it has a lot of missing pieces. Its currently in desse-dynamic branch.

[devashishdxt]

Implemented DesseDynamic for Option<T> in 4a0239b.