Add a stable diffusion example (#328)

* Start adding a stable-diffusion example.

* Proper computation of the causal mask.

* Add the chunk operation.

* Work in progress: port the attention module.

* Add some dummy modules for conv2d and group-norm, get the attention module to compile.

* Re-enable the 2d convolution.

* Add the embeddings module.

* Add the resnet module.

* Add the unet blocks.

* Add the unet.

* And add the variational auto-encoder.

* Use the pad function from utils.

candle-examples/examples/stable-diffusion/main.rs

@@ -0,0 +1,30 @@
+#[cfg(feature = "mkl")]
+extern crate intel_mkl_src;
+
+mod attention;
+mod clip;
+mod embeddings;
+mod resnet;
+mod unet_2d;
+mod unet_2d_blocks;
+mod utils;
+mod vae;
+
+use anyhow::Result;
+use clap::Parser;
+
+#[derive(Parser, Debug)]
+#[command(author, version, about, long_about = None)]
+struct Args {
+    /// Run on CPU rather than on GPU.
+    #[arg(long)]
+    cpu: bool,
+
+    #[arg(long)]
+    prompt: String,
+}
+
+fn main() -> Result<()> {
+    let _args = Args::parse();
+    Ok(())
+}