Update donation webhook payload example for webhook v2.
Update donations webhook json to include rnc id and rnc registration id descriptions for the donor.
Fill in more json fields in the donations webhook example.
List the previous donation webhook payload sample in the webhook documentation.
Merge branch 'master' of github.com:3dna/api_docs into miki/update_donation_webhook_doc
Merge pull request #4 from 3dna/miki/update_donation_webhook_doc

Update donation webhook payload example for webhook v2