Add jsgo.io example

jsgo/main.go

@@ -0,0 +1,20 @@
+// +build js,wasm
+
+package main
+
+import "syscall/js"
+
+var document js.Value
+
+func init() {
+	document = js.Global().Get("document")
+}
+
+func main() {
+	div := document.Get("body")
+
+	node := document.Call("createElement", "div")
+	node.Set("innerHTML", "Hello jsgo.io!")
+
+	div.Call("appendChild", node)
+}