Initial example of using the WebAudio APIs from web-sys

Part of #443

examples/webaudio/index.js

@@ -0,0 +1,40 @@
+const rust = import('./webaudio');
+
+
+// Most browsers don't let WebAudio autoplay without some interaction from the user.  So once the module is loaded,
+// it's passed to this function which will set up the UI elements for the user to interact with
+function setup(rust_module) {
+    play = function() {
+            console.log("About to create some music!");
+            fm = new rust_module.FmOsc();
+
+            fm.set_note(50);
+            fm.set_fm_frequency(0);
+            fm.set_fm_amount(0);
+            fm.set_gain(0.8);
+
+    };
+
+    // create some UI elements
+    const primary_slider = document.getElementById("primary_input");
+    primary_slider.oninput = (e) => {
+        fm.set_note(e.target.value);
+    };
+
+    const fm_freq = document.getElementById("fm_freq");
+    fm_freq.oninput = (e) => {
+        fm.set_fm_frequency(e.target.value);
+    };
+
+    const fm_amount = document.getElementById("fm_amount");
+    fm_amount.oninput = (e) => {
+        fm.set_fm_amount(e.target.value);
+    };
+
+    console.log("Ready!  Press the play button!");
+}
+
+
+rust.then(m => {
+    setup(m);
+});