Update gitignore for Visual Studio 2019

Default behaviour of VS2019 "Open Folder" for cmake projects:
- Build into "out/" folder in-source
- Store the config in CMakeSettings.json
- Keep VS info in .vs/ folder

.gitignore

@@ -18,6 +18,9 @@ build
 *.VC.db-wal
 *.VC.opendb
 *.ipch
+.vs/
+out/
+CMakeSettings.json
 
 # Output
 bin/