add a patched kernel.json (enabling preview features)

Author: forax

kernel.json

@@ -0,0 +1,15 @@
+{
+    "argv": [
+        "java",
+        "--enable-preview",
+        "-jar",
+        "@KERNEL_INSTALL_DIRECTORY@/ijava-1.3.0.jar",
+        "{connection_file}"
+    ],
+    "display_name": "Java",
+    "language": "java",
+    "interrupt_mode": "message",
+    "env": {
+        
+    }
+}