Update Filecoin Pay cookbook

[BigLep]

Done Criteria

https://github.com/FilOzone/synapse-sdk/blob/master/docs/src/content/docs/cookbooks/filecoin-pay.mdx is updated to include relevant parts from https://hackmd.io/@lordforever/SJ6Lwv2dWx

Why Important

Enable developers to be more self-service to understand filecoin-pay within FWSS.
Take advantage of recent great docs in hackmd that aren't as discoverable currently.

[BigLep]

@nijoe1 : when will you be able to take this? We have this listed for M4.1.