Add a "hello world" style program

src/main_blink.cc

@@ -0,0 +1,16 @@
+#include "daisy_seed.h"
+
+namespace ld = daisy;
+
+static ld::DaisySeed hw{};
+
+int main()
+{
+    hw.Init();
+    while (true) {
+        hw.SetLed(true);
+        hw.DelayMs(100);
+        hw.SetLed(false);
+        hw.DelayMs(100);
+    }
+}