Update eslint rules.

.eslintrc.cjs

@@ -5,12 +5,28 @@
 module.exports = {
 	extends: 'ckeditor5',
 	root: true,
+	ignorePatterns: [
+		// Ignore the entire `build/` (the DLL build).
+		'build/**',
+		// Ignore the entire `dist/`.
+		'dist/**'
+	],
 	rules: {
 		// This rule disallows importing core DLL packages directly. Imports should be done using the `ckeditor5` package.
 		// Also, importing non-DLL packages is not allowed. If the package requires other features to work, they should be
 		// specified as soft-requirements.
 		// Read more: https://ckeditor.com/docs/ckeditor5/latest/builds/guides/migration/migration-to-26.html#soft-requirements.
-		'ckeditor5-rules/ckeditor-imports': 'error'
+		'ckeditor5-rules/ckeditor-imports': 'error',
+		//  This rule disallows importing from any path other than the package main entrypoint.
+		'ckeditor5-rules/allow-imports-only-from-main-package-entry-point': 'error',
+		// As required by the ECMAScript (ESM) standard, all imports must include a file extension.
+		// If the import does not include it, this rule will try to automatically detect the correct file extension.
+		'ckeditor5-rules/require-file-extensions-in-imports': [
+			'error',
+			{
+				extensions: [ '.ts', '.js', '.json' ]
+			}
+		]
 	},
 	overrides: [
 		{
@@ -21,11 +37,5 @@ module.exports = {
 				'ckeditor5-rules/ckeditor-imports': 'off'
 			}
 		}
-	],
-	ignorePatterns: [
-		// Ignore the entire `build/` (the DLL build).
-		'build/**',
-		// Ignore the entire `dist/`.
-		'dist/**'
 	]
 };

package.json

@@ -39,7 +39,7 @@
     "@ckeditor/ckeditor5-package-tools": "^2.0.0-alpha.0",
     "ckeditor5": "nightly",
     "eslint": "^7.32.0",
-    "eslint-config-ckeditor5": ">=3.1.1",
+    "eslint-config-ckeditor5": "^6.0.0",
     "http-server": "^14.1.0",
     "husky": "^4.2.5",
     "lint-staged": "^10.2.6",