Add PaliGemma. (#2519)

* Add PaliGemma.

* PaliGemma inference loop.

* Running PaliGemma example.

* Tweak the prompt.

candle-examples/examples/paligemma/README.md

@@ -0,0 +1,28 @@
+# PaliGemma
+
+[HuggingFace Model Card](https://huggingface.co/google/paligemma-3b-pt-224) -
+[Model Page](https://ai.google.dev/gemma/docs/paligemma)
+
+```bash
+cargo run --features cuda --release --example paligemma -- \
+    --prompt "caption fr" --image candle-examples/examples/yolo-v8/assets/bike.jpg
+```
+
+```
+loaded image with shape Tensor[dims 1, 3, 224, 224; bf16, cuda:0]
+loaded the model in 1.267744448s
+caption fr. Un groupe de cyclistes qui sont dans la rue.
+13 tokens generated (56.52 token/s)
+```
+
+```bash
+cargo run --features cuda --release --example paligemma -- \
+    --prompt "caption fr" --image candle-examples/examples/flux/assets/flux-robot.jpg
+```
+
+```
+loaded image with shape Tensor[dims 1, 3, 224, 224; bf16, cuda:0]
+loaded the model in 1.271492621s
+caption fr une image d' un robot sur la plage avec le mot rouillé
+15 tokens generated (62.78 token/s)
+```