gitignore: Add vscode folder.

.gitignore

 # exclude top level directories
 # which are taken from other git repositories
 # The / at the beginning is important, otherwise all directories
-# containing the string are ignored 
+# containing the string are ignored
 /geometry
 /input
 /parameters
@@ -12,3 +12,6 @@ Dart*.cfg
 
 # gdb Crash dumps
 **/core_dump_*
+
+# IDEs
+.vscode