Add Limestone attack stone to skill calc

This is apparently method for UIM to train construction so it is
probably very useful to have.

Signed-off-by: Tomas Slusny <slusnucky@gmail.com>

runelite-client/src/main/resources/net/runelite/client/plugins/skillcalculator/skill_construction.json

@@ -756,6 +756,12 @@
       "name": "Teak Demon Lectern",
       "xp": 180
     },
+    {
+      "level": 59,
+      "icon": 8154,
+      "name": "Limestone attack stone",
+      "xp": 200
+    },
     {
       "level": 59,
       "icon": 8343,