add reference to built-in validation rules

Author: zamronypj

documentation/index.md

@@ -37,7 +37,7 @@ description: Documentation and developer's resources for Fano Framework, web app
 ## Security
 
 - **[Handling CORS](/security/handling-cors)** discusses how to handle *Cross-origin Resource Sharing (CORS)* issue in Fano Framework.
-- **[Form Validation](/security/form-validation)**. It explains how to validate form input data.
+- **[Form Validation](/security/form-validation)**. It explains how to validate form input data including how to use [built-in validation rules](/security/form-validation/built-in-validation-rules/) or [creating your own validation rule]((/security/form-validation#writing-your-own-validation-rule)).
 - **[CSRF Protection](/security/csrf-protection)** discusses how to protect application from *Cross-site request Forgery (CSRF)* attack.
 - **[HTTP Verb Tunnelling](/security/http-verb-tunnelling)** explains about how to override HTTP verb such as `PUT`, `PATCH` and `DELETE`.
 - **[HTTP Authentication](/security/http-authentication)** discusses authentication using basic, digest, bearer token authentication. It is also related to JSON Web Token.

security/form-validation/index.md

@@ -206,11 +206,11 @@ Please note that `lastValidationResult()` return last validation status so, abov
 
 `lastValidationResult()` method is provided so developer can execute validation in middleware and later in controller inspects last validation status and act accordingly.
 
-## <a name="built-in-validation-rule"></a>Built-in validation rule
+## <a name="built-in-validation-rule"></a>Built-in validation rules
 
 Fano Framework comes with several built-in validation rules, some are validation rule mentioned in above code example. Read [Built-in Validation Rules](/security/form-validation/built-in-validation-rules) for more information.
 
-## Writing your own validation rule
+## <a name="writing-your-own-validation-rule">Writing your own validation rule
 
 If built-in validation rules do not meet your requirement, you can create your own validation rule by creating class that implements `IValidator`.