add speech recognition (#75)

extensions/Speech/extension.json

@@ -0,0 +1,4 @@
+{
+    "description": "Blocks for speech recognition and synthesis",
+    "useDev": false
+}

extensions/Speech/index.js

@@ -0,0 +1,74 @@
+(function () {
+    const I32_MAX = 2147483647;
+
+    class Speech extends Extension {
+        constructor(ide) {
+            super('Speech');
+            this.ide = ide;
+
+            this.SpeechRecognition = window.SpeechRecognition || window.webkitSpeechRecognition;
+            this.requestQueue = [];
+
+            if (this.SpeechRecognition) {
+                this.recognizer = new this.SpeechRecognition();
+
+                this.recognizer.continuous = false;
+                this.recognizer.lang = 'en-US';
+                this.recognizer.interimResults = false;
+                this.recognizer.maxAlternatives = 1;
+
+                this.recognizer.onstart = (e) => {
+                    this.recognized = '';
+                };
+                this.recognizer.onresult = (e) => {
+                    this.recognized = ((e.results || [])[0] || [])[0]?.transcript || '';
+                };
+                this.recognizer.onend = (e) => {
+                    const requests = this.requestQueue;
+                    this.requestQueue = [];
+                    for (const req of requests) {
+                        req(this.recognized);
+                    }
+                };
+            }
+        }
+
+        getMenu() {
+            return {};
+        }
+
+        getCategories() {
+            return [];
+        }
+
+        getPalette() {
+            const blocks = [
+                new Extension.Palette.Block('speechRecognize'),
+            ];
+            return [
+                new Extension.PaletteCategory('sensing', blocks, SpriteMorph),
+                new Extension.PaletteCategory('sensing', blocks, StageMorph),
+            ];
+        }
+
+        getBlocks() {
+            const thisExtension = this;
+            return [
+                new Extension.Block('speechRecognize', 'reporter', 'sensing', 'listen for speech', [],
+                    function () {
+                        return this.runAsyncFn(async () => {
+                            return await new Promise((resolve, reject) => {
+                                thisExtension.requestQueue.push(resolve);
+                                try {
+                                    thisExtension.recognizer.start();
+                                } catch (e) {}
+                            });
+                        }, { timeout: I32_MAX })
+                    },
+                ).for(SpriteMorph, StageMorph),
+            ];
+        }
+    }
+
+    NetsBloxExtensions.register(Speech);
+})();