fix(gitignore): add .vs folder to .gitignore

.vs folder is the folder created automatically during opening the project in Visual Studio.
Visual Studio uses the folder to store opened documents, breakpoints, machine- and user-specific files and other information about state of the solution.
So this folder should be added to .gitignore

Author: MrVitaly

.gitignore

@@ -1,2 +1,3 @@
 # Make sure nupkg files don't get pushed to git repo
-**/*.nupkg
+**/*.nupkg
+/.vs