Frequency Graph User Data

[wilwade]

Problem

Update the Frequency Implementation post #233 and #226

Closes #239

Solution

• Added Frequency/UserData.md
• Added PublicKey Announcement
• Added information about the Stateful Storage Pallet
• Updated other related tables.

[shannonwells]

Looks good, I just had a tiny suggestion that is non-blocking.

[aramikm]

After looking into the details of how libsodium library and how it needs to get build on each platform and architecture differently and considering that we would need to create bridges for our Rust library on top of this, then it's self evident that how complicated this might become.
I'm recommending to use a Rust native implementation of libsodium. crypto_box crate has the same seal and unseal functionality which is compatible with libsodium.
Other functionalities used in libsodium like crypto_box_beforenm and crypto_kdf_derive_from_key, crypto_secretbox_detached are kinda very niche use-cases and not directly implemented in it but we can reach the same result (more or less) with some other Rust libraries.

In general I'm suggesting to use more mainstream functions and definitions for above functionalities if possible.

[aramikm]

Looks good! I added a couple of questions and comments.