examples: add example for use with wasm-unknown target

Signed-off-by: deadprogram <ron@hybridgroup.com>

src/examples/hello-wasm-unknown/main.go

@@ -0,0 +1,18 @@
+// this is intended to be used as wasm32-unknown-unknown module.
+// to compile it, run:
+// tinygo build -size short -o hello-unknown.wasm -target wasm-unknown -gc=leaking -no-debug ./src/examples/hello-wasm-unknown/
+package main
+
+var x int32
+
+//go:wasmimport hosted echo_i32
+func echo(x int32)
+
+//go:export update
+func update() {
+	x++
+	echo(x)
+}
+
+func main() {
+}