ADD: Master Readme improvements

[thorchain-admin]

Current

The master readme is light on docs/examples. The instructions are in the /package/<client>/readme but not obvious for new users

Desired

Have a very enticing master readme:

• install instructions
• Simple overview
• Various examples and walkthroughs (for any client, any function)
• With links that point deeper into packages
• Pretty pictures and logos and emojis

Good example: https://github.com/cosmostation/cosmosjs