Derive Default for CodeActionOptions

[Jamalam360]

Every field in this struct already implements Default, I don't see why this one doesn't - especially when a lot of the other option structs have a default.

https://github.com/gluon-lang/lsp-types/blob/master/src/code_action.rs#L349

I'm sure there are other instances of this in the code base as well.

Thanks