Update _sidebar

_sidebar.md

@@ -1,18 +1,18 @@
-- [Home](Home)
-- [Vision document](Vision Document)
+- [Home](home)
+- [Vision document](vision-document)
 - Requirements
-  - [Use-Case Diagram](Use-Case Diagram)
-  - [Use-Cases](Use-Cases)
-  - [Domain Model](Domain Model)
-  - [Sequence Diagrams](Sequence Diagrams)
-  - [Wireframe](Wireframe)
-  - [Usability Tests](Usability Test)
-  - [Universal Design](Universal Design)
+  - [Use-Case Diagram](use-case-diagram)
+  - [Use-Cases](use-cases)
+  - [Domain Model](domain-model)
+  - [Sequence Diagrams](sequence-diagrams)
+  - [Wireframe](wireframe)
+  - [Usability Tests](usability-tests)
+  - [Universal Design](universal-design)
 - System
-  - [Project Structure](Project Structure)
-  - [Class Diagram](Class Diagram)
-  - [Persistence](Persistence)
-  - [Source Code](Source Code)
-  - [Installation Manual](Installation Manual)
-  - [User Manual](User Manual)
-  - [Testing](Testing)
+  - [Project Structure](project-structure)
+  - [Class Diagram](class-diagram)
+  - [Persistence](persistence)
+  - [Source Code](source-code)
+  - [Installation Manual](installation-manual)
+  - [User Manual](user-manual)
+  - [Testing](testing)