[docs] custom script examples, [build] move CMS make to app via event_handlers.on_build

docs/dev/custom_script_examples/docs.dev.custom_script.item_code.md

@@ -0,0 +1,35 @@
+---
+{
+	"_label": "Generate Item Code based on Custom Logic"
+}
+---
+Add this in the Custom Script of **Item**, so that the new Item Code is generated just before the a new Item is saved.
+
+	cur_frm.cscript.custom_validate = function(doc) {
+	    // clear item_code (name is from item_code)
+	    doc.item_code = "";
+
+	    // first 2 characters based on item_group
+	    switch(doc.item_group) {
+	        case "Test A":
+	            doc.item_code = "TA";
+	            break;
+	        case "Test B":
+	            doc.item_code = "TB";
+	            break;
+	        default:
+	            doc.item_code = "XX";
+	    }
+
+	    // add next 2 characters based on brand
+	    switch(doc.brand) {
+	        case "Brand A":
+	            doc.item_code += "BA";
+	            break;
+	        case "Brand B":
+	            doc.item_code += "BB";
+	            break;
+	        default:
+	            doc.item_code += "BX";
+	    }
+	}