Implement stub for number and add blocks

src/blocks/scratch3_operators.js

@@ -0,0 +1,29 @@
+function Scratch3OperatorsBlocks(runtime) {
+    /**
+     * The runtime instantiating this block package.
+     * @type {Runtime}
+     */
+    this.runtime = runtime;
+}
+
+/**
+ * Retrieve the block primitives implemented by this package.
+ * @return {Object.<string, Function>} Mapping of opcode to Function.
+ */
+Scratch3OperatorsBlocks.prototype.getPrimitives = function() {
+    return {
+        'math_number': this.number,
+        'math_add': this.add
+    };
+};
+
+
+Scratch3OperatorsBlocks.prototype.number = function(args) {
+    return Number(args.NUM);
+};
+
+Scratch3OperatorsBlocks.prototype.add = function(args) {
+    return args.NUM1 + args.NUM2;
+};
+
+module.exports = Scratch3OperatorsBlocks;

src/engine/runtime.js

@@ -6,6 +6,7 @@ var util = require('util');
 var defaultBlockPackages = {
     'scratch3_control': require('../blocks/scratch3_control'),
     'scratch3_event': require('../blocks/scratch3_event'),
+    'scratch3_operators': require('../blocks/scratch3_operators'),
     'wedo2': require('../blocks/wedo2')
 };