Document how to connect to chain with JS app

[ethanfrey]

Add some general documention around the work in #2 explaining how to configure and use CosmJS and connect Keplr.
Reference any existing documentation for those and link to them.
Include a few basic code samples in the doc, but no need to copy anything that can be found elsewhere and linked.

This should be designed to onboard people who have never used CosmJS or Cosmos before (and more used to Ethereum tooling). It should be a quick start to get going and show where to find more information on the various functions they will want to use to interact with AVSes (set up wallet, cosmwasm query and message, bamk query and message).

If not too hard, explain how this can be used in node.js apps as well

[msteiner96]

Hi @ethanfrey , isnt this quite redundant with https://github.com/Lay3rLabs/docs-avs/issues/3 ?

[ethanfrey]

Kinda, but they are slightly distinct in my mind.

I meant #3 to be more how to install Keplr and connect as a user.
And #5 to be how to create a SigningClient in CosmJS code sample (with link to your code in example-avs-ui)

They can easily both be closed with one docs PR