Update Todoist.Net version to 6.1.0

The version prefix for the Todoist.Net project has been updated. This change moves the version from 6.0.0 to 6.1.0.

Author: olsh

src/Todoist.Net/Todoist.Net.csproj

@@ -2,7 +2,7 @@
 
   <PropertyGroup>
     <Description>A Todoist API client for .NET</Description>
-    <VersionPrefix>6.0.0</VersionPrefix>
+    <VersionPrefix>6.1.0</VersionPrefix>
     <Authors>Oleg Shevchenko</Authors>
     <TargetFrameworks>netstandard2.0;net45</TargetFrameworks>
     <GenerateDocumentationFile>true</GenerateDocumentationFile>