Add a foreach_add helper function

src/helpers/generic-helpers.scad

@@ -173,6 +173,17 @@ function affine_scale(vector) = [
     [0, 0, 0, 1]
 ];
 
+/**
+ * @brief Add something to each element in a list.
+ * @param list The list whos elements will be modified.
+ * @param to_add
+ * @returns a list with `to_add` added to each element in the list.
+ */
+function foreach_add(list, to_add) =
+    assert(is_list(list))
+    assert(!is_undef(to_add))
+    [for (item = list) item + to_add];
+
 /**
  * @brief Create a rectangle with rounded corners by sweeping a 2d object along a path.
  * @Details Centered on origin.