Use types provided by '@types/libsodium-wrappers' instead of declaring sodium as 'any'

[Arxcis]

NB!: I have not discussed this change with anyone yet, so please voice your oppinion :pray:

Motivation

Since this repo is a typescript repo, and it relies heavily on libsodium-wrappers, it would be nice to have types. As a newcomer to the code, it was difficult to understand the integration with libsodium-wrappers, when every value and function-call was declared as any.

Demo

Before (with any)	After (with types)
(property) DIDComm.sodium: any	(property) DIDComm.sodium: typeof sodium