feat: add difftastic and delta to jj-toolchain

Author: sigma

packages/jj-toolchain/data.json

@@ -4,6 +4,8 @@
     "jj": "0.40.0",
     "jjui": "0.10.2",
     "git": "2.53.0",
-    "gh": "2.90.0"
+    "gh": "2.90.0",
+    "difftastic": "0.68.0",
+    "delta": "0.19.2"
   }
 }