Docs: Add working groups to maintainer guide

docs/maintainer-guide/README.md

@@ -17,3 +17,7 @@ Describes how to do an ESLint project release.
 ## [Governance](governance.md)
 
 Describes the governance policy for ESLint, including the rights and privileges of individuals inside the project.
+
+## [Working Groups](working-groups.md)
+
+Describes how working groups are created and how they function within the ESLint project.

docs/maintainer-guide/working-groups.md

@@ -0,0 +1,22 @@
+# Working Groups
+
+The ESLint TSC may form working groups to focus on a specific area of the project.
+
+## Creating a Working Group
+
+Working groups are created by sending an email to the team mailing list. Each working group:
+
+1. Must have a GitHub team under the "ESLint Team" top-level GitHub team. (The GitHub team name should end with "WG" to distinguish it from other types of teams.)
+1. Must have at least one TSC member.
+1. May have any number of Committers and Reviewers.
+1. Must have at least two members.
+
+Active working groups are listed on the [team page](https://eslint.org/team).
+
+## How Working Groups Work
+
+Each working group is responsible for its own inner working. Working groups can decide how large or small they should be (so long as there is at least two members), when and who to add or remove from the working group, and how to accomplish their objectives.
+
+Working groups may be temporary or permanent.
+
+If working groups intend to make a significant change to the ESLint project, the proposal must still be approved by the TSC.