docs: list recommended Conventional Commit scopes

Author: wincent

CONTRIBUTING.md

@@ -21,3 +21,23 @@ These apply to any work at Liferay, including in this monorepo:
 -   [Creating a project](CONTRIBUTING/creating-a-project.md)
 -   [Importing a project](CONTRIBUTING/importing-a-project.md)
 -   [Migrating an npm package to the `@liferay` named scope](CONTRIBUTING/migrating-an-npm-package-to-the-liferay-named-scope.md)
+
+## Conventional commit scopes
+
+It is helpful to include [an optional scope in your commit messages](guidelines/general/commit_messages.md) so that people can see, at a glance, which commits affect which projects. Valid scopes correspond to project names such as:
+
+-   `eslint-config`
+-   `js-themes-toolkit`
+-   `js-toolkit`
+-   `npm-tools`
+
+And package names such as:
+
+-   `changelog-generator`
+-   `js-publish`
+-   `npm-scripts`
+-   `workspace-scripts`
+
+As well as the scope of `monorepo` to label cross-cutting changes that affect multiple projects and packages in the monorepo.
+
+**NOTE:** The preceding lists are non-exhaustive and for illustration purposes.