docs: Add note about OpenCollective bot (#1580)

CONTRIBUTING.md

@@ -20,6 +20,7 @@ Please note that this project is released with a [Contributor Code of Conduct](.
 - [GitHub Apps](#github-apps)
 - [Becoming a maintainer](#becoming-a-maintainer)
 - [Who is funding work on Nock?](#who-is-funding-work-on-nock)
+- [Priority Support](#priority-support)
 - [Is there a chat where I can talk to other maintainers and users?](#is-there-a-chat-where-i-can-talk-to-other-maintainers-and-users)
 
 <!-- tocstop -->
@@ -150,6 +151,10 @@ Nock is entirely self-funded by [our Open Collective](https://opencollective.com
 
 If you'd like to give money to support Nock, please do go to our profile and check it out.
 
+## Priority Support
+
+As part of backing on Open Collective, we tag some issues as a priority if the user who opens them is also a backer, using the [Open Collective Bot](https://github.com/marketplace/open-collective-bot). In general, as maintainers we will give priority to support people who are working on these issues. The money in the Open Collective goes to the entire project, however, and maintainers are volunteers.
+
 ## Is there a chat where I can talk to other maintainers and users?
 
 We don't have a chat for a variety of reasons - mainly, because our maintainers' time is limited, and we don't want to be on the hook for enforcing codes of conduct or for checking in every day. However, we encourage you to open issues about anything related to Nock! Issues really are the best way to keep the conversation focused on development.