Fix VS Code launching in wrong folder (#66)

It appears that a backslash in the working directory (in "launch.json") is not correctly handled by the Java launcher or so, causing the game to run in the workspace folder instead of "run".

src/main/java/net/fabricmc/loom/task/GenVsCodeProjectTask.java

@@ -87,7 +87,7 @@ public class GenVsCodeProjectTask extends DefaultLoomTask {
         public String type = "java";
         public String name;
         public String request = "launch";
-        public String cwd = "${workspaceFolder}\\run";
+        public String cwd = "${workspaceFolder}/run";
         public String console = "internalConsole";
         public boolean stopOnEntry = false;
         public String mainClass;