Docs: Changelog. [skip ci]

CHANGELOG.md

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 Changelog
 =========
 
+## [4.0.0](https://github.com/ckeditor/ckeditor5-inspector/compare/v3.1.1...v4.0.0) (2022-04-12)
+
+### BREAKING CHANGES
+
+* Due to introducing the lock mechanism for the `Editor#isReadOnly` property, the inspector uses the new way of enabling the read-only mode in the editor. It requires an instance of CKEditor 5 in version 34 or higher. See [ckeditor/ckeditor5#10496](https://github.com/ckeditor/ckeditor5/issues/10496).
+
+### Other changes
+
+* Aligned the CKEditor 5 Inspector API to use the new lock mechanism when enabling/disabling the read-only mode. ([commit](https://github.com/ckeditor/ckeditor5-inspector/commit/55d72a3a8f708554d22341ce26a31f4448c39fc5))
+
+
 ## [3.1.1](https://github.com/ckeditor/ckeditor5-inspector/compare/v3.1.0...v3.1.1) (2022-03-29)
 
 ### Bug fixes