Add IE structural arm convenience recipes

kubejs/server_scripts/recipes/structural_arm.js

@@ -0,0 +1,12 @@
+// priority: 0
+
+onEvent("recipes", event => {
+  // See `recipes/essentials/stairs.js` for comments.
+  event.forEachRecipe({ id: /^immersiveengineering:crafting\/.*_slope$/ }, recipe => {
+    let input  = recipe.inputItems[0];
+    let output = recipe.outputItems[0].getId();
+    recipe.replaceOutput(output, "6x " + output, false, (out, orig) => out);
+    event.shaped("3x " + output, [ "BB", "B " ], { B: input });
+    event.shapeless(input, [ output ]);
+  });
+});