Update version to 2.0.0

Author: miniwolf

Changelog.txt

@@ -6,6 +6,12 @@ Git: https://github.com/Unity-Technologies/vscode-unity-debug
 Changes
 -------
 
+2.0.0
+=====
+ - Updated packages to support .NET 4.6 runtime in Unity.
+ - Fix issue with being able to detach from Unity, which would cause the Unity Editor to hang.
+ - Various instabilities fixes, such as LINQ debugging for .NET 4.6 runtime, hovering variables, complex class debugging etc.
+
 1.3.0
 =====
  - Fix "Error: command 'vscode.startDebug' not found" error when using "Unity Attach Debugger" command.