update readme.md

README.md

@@ -234,11 +234,14 @@ Additionally to all the methods declared in the [Parser-API](https://github.com/
 [Spectral](https://github.com/stoplightio/spectral) powers the validation of AsyncAPI documents within ParserJS. 
 The default [built-in rulesets](src/ruleset) are:
 
-- Core ruleset. Basic and global validation. Apply to all AsyncAPI Spec versions (with some exceptions).
-- Recommended ruleset. These are good practices. They won't create validation errors but warnings.
-- Specific rulesets per each AsyncAPI Spec version. Contain particular rulesets that apply only to documents of a particular Spec version.
-  - Core rulesets: Rules that generate validation errors if not fulfilled by a particular Spec version.
-  - Recommended rulesets: Best practices for a particular Spec version
+- Core ruleset:
+  - Basic and global validation. Apply to all AsyncAPI Spec versions (with some exceptions).
+- Recommended ruleset:
+  - These are good practices. They won't create validation errors but warnings.
+- Specific rulesets per each AsyncAPI Spec version:
+  - Contain particular rulesets that apply only to documents of a particular Spec version:
+    - Core rulesets: Rules that generate validation errors if not fulfilled by a particular Spec version.
+    - Recommended rulesets: Best practices for a particular Spec version
 
 It is possible to use your rulesets/rules or overwrite existing ones, passing the `ruleset` option to the Parser instance: