basic state machines (#72)

extensions/StateMachine/extension.json

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+{
+    "description": "create and visualize state machines",
+    "useDev": false
+}

extensions/StateMachine/index.js

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+(function () {
+    class StateMachine extends Extension {
+        constructor(ide) {
+            super('StateMachine');
+        }
+
+        getMenu() {
+            return {
+                'visualize': function () {
+                    alert('Coming Soon!');
+                },
+            };
+        }
+
+        getCategories() {
+            return [
+                new Extension.Category('StateMachine', new Color(150, 150, 150)),
+            ];
+        }
+
+        getPalette() {
+            const blocks = [
+                new Extension.Palette.Block('smTransition'),
+                new Extension.Palette.Block('smInState'),
+            ];
+            return [
+                new Extension.PaletteCategory('StateMachine', blocks, SpriteMorph),
+                new Extension.PaletteCategory('StateMachine', blocks, StageMorph),
+            ];
+        }
+
+        getBlocks() {
+            return [
+                new Extension.Block('smTransition', 'command', 'StateMachine', 'transition %var to %s', [], function (machine, state) {
+                    this.doSetVar(machine, state);
+                    this.doStop();
+                }).terminal().for(SpriteMorph, StageMorph),
+                new Extension.Block('smInState', 'predicate', 'StateMachine', '%var in state %s ?', [], function (machine, state) {
+                    const variables = this.context.variables;
+                    return variables.getVar(machine) == state;
+                }).for(SpriteMorph, StageMorph),
+            ];
+        }
+    }
+
+    NetsBloxExtensions.register(StateMachine);
+})();