4.28.0 (2021-06-21)

Bug Fixes

• eslint-plugin: [prefer-regexp-exec] factor in union types (#3434) (ac86a79)
• experimental-utils: expand RuleTester config properties (#3557) (ffbb3cf)
• experimental-utils: fix eslint-utils' negative predicates' return types (#3462) (1e6016b)
• experimental-utils: fix eslint-utils' negative predicates' return types in ast-utils (#3461) (614b0a3)
• experimental-utils: make keys for ReferenceTracker options optional (#3531) (a7fd7bb)

Features

• experimental-utils: add only property to RuleTester types (#3555) (2a36e3e)
• experimental-utils: expose ReferenceTracker.ESM (#3532) (4ac67c4)
• experimental-utils: use mergable interface for settings property (#3556) (abfc19b)