Document Lens+Livepeer SDK

[victorges]

https://www.notion.so/livepeer/Lens-Integration-e756c036e6c741de97d8e9ef1c351e84#0fd96f1b6a8448f89dca793ee6f90083

Will involve actually dogfooding the SDK for a good guide for users. It is a higher-level documentation on how to use the SDK to mint Lens publications.
- This is different than code documentation, which should be included in livepeer/task-runner#33. It’s meant for a guide like How to Mint a Video NFT but specific for Lens developers.

Definitions of done:

1. Can read through a guide with no previous knowledge about Livepeer, Lens or the SDK and come out with a sample application or just a simple integration with Lens
2. Output integration should be able to create Lens posts and display them as video players