ICS010: Update to the new BEEFY protocol

[en]

Hi all!

Since the BEEFY protocol was designed, implementing a light client based on GRANDPA directly is not the best option. We updated the spec to take advantage of the new protocol.

And I updated the author's contact emails:

• Replaced my email with [email protected]
• Removed John
• Added Rivers Yang. He is leading a team to implement IBC on NEAR.

[AdityaSripal]

Hi could you give this a review @seunlanlege?

[seunlanlege]

Doesn't really need my input @AdityaSripal