Add a specific example for cuda.

examples/cuda_basics.rs

@@ -0,0 +1,9 @@
+use anyhow::Result;
+use candle::{DType, Device, Tensor};
+
+fn main() -> Result<()> {
+    let device = Device::new_cuda(0)?;
+    let x = Tensor::zeros(4, DType::F32, device)?;
+    println!("{:?}", x.to_vec1::<f32>()?);
+    Ok(())
+}