Generate Hello world pages for the DIDComm v2 book

[2byrds]

Hello World documentation for the DIDComm v2 book is outlined in the README

@dhh1128 gave us additional directions in the unsync as follows:

1. look at the IIW slides that was given by DSR in Oct 2021. The actual narration/video of their presentation might be (more) helpful....
   Here is a recording that goes along with the PPT and the demo code from DSR, that might be useful in Hello World.
   They walked people through sending and receiving a message. You could possibly link to their recording as an extra resource, and/or use the same workflow. One nice thing about it is that the libraries they used have the same interface in 3 or 4 different programming languages, so the Hello World writeup could be almost identical no matter which language a programmer likes.
2. Seed documentation from that demo and presentation that shows a sender in python and a receiver in java. https://github.com/sicpa-dlab/didcomm-demo/blob/main/didcomm-demo-python/didcomm_demo/didcomm_demo.py
3. Since they gave this preso, they finished the Rust work, and they have a wrapper for WASM and Swift, so JavaScript (browser, server-side) and iOS are now possible targets for the same demo.