[EXAMPLE] add cross compilation example

examples/nrf52840/blinky/src/main.rs

diff --git a/examples/nrf52840/blinky/src/main.rs b/examples/nrf52840/blinky/src/main.rs
new file mode 100644
index 0000000..6cf1cce
--- /dev/null
+++ b/examples/nrf52840/blinky/src/main.rs
@@ -0,0 +1,20 @@
+#![no_std]
+#![no_main]
+
+use embassy_executor::Spawner;
+use embassy_nrf::gpio::{Level, Output, OutputDrive};
+use embassy_time::Timer;
+use {defmt_rtt as _, panic_probe as _};
+
+#[embassy_executor::main]
+async fn main(_spawner: Spawner) {
+    let p = embassy_nrf::init(Default::default());
+    let mut led = Output::new(p.P0_26, Level::Low, OutputDrive::Standard);
+
+    loop {
+        led.set_high();
+        Timer::after_millis(300).await;
+        led.set_low();
+        Timer::after_millis(300).await;
+    }
+}