Update _sidebar

_sidebar.md

@@ -1,18 +1,18 @@
-- [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)
-- 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)
+[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)
+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)