Fix broken doc link in README (#1735)

README.md

@@ -39,7 +39,7 @@ Table of Contents
 
 Introduction
 ============
-PSScriptAnalyzer is a static code checker for PowerShell modules and scripts. PSScriptAnalyzer checks the quality of PowerShell code by running a [set of rules](RuleDocumentation).
+PSScriptAnalyzer is a static code checker for PowerShell modules and scripts. PSScriptAnalyzer checks the quality of PowerShell code by running a [set of rules](docs/Rules).
 The rules are based on PowerShell best practices identified by PowerShell Team and the community. It generates DiagnosticResults (errors and warnings) to inform users about potential
 code defects and suggests possible solutions for improvements.