Add return types to *.pyi stubs (#880)

* Start generating return types

* Finish tensor type hinting

* Add `save_gguf` to `utils`

* Typehint `quant-llama.py`

candle-pyo3/py_src/candle/__init__.py

@@ -1 +1,5 @@
-from .candle import *
+from .candle import *
+
+__doc__ = candle.__doc__
+if hasattr(candle, "__all__"):
+    __all__ = candle.__all__