Update 00-intro.md

Author: nyamsprod

docs/00-intro.md

@@ -57,7 +57,7 @@ composer require bakame/http-structured-fields
 - [Basic usage](01-basic-usage.md)
 - [Parsing and Serializing](02-parsing-serializing.md)
 - [Structured Field Value Types](03-value-types.md)
-- [Structured Field Item Data Type](04-item.md)
-- [Structured Field Containers Data Type](05-containers.md)
-- [Structured Field Validation](06-validation.md)
+- [The Item Data Type](04-item.md)
+- [The Structured Field Containers](05-containers.md)
+- [HTTP Fields Validation](06-validation.md)
 - [Interacting with the PHP Ecosystem](07-extensions.md)