Add note about MLIR compiled outputs in dev docs

Adding an example on how to extract MLIR output from the compilation
process in various different formats to the development documentation.

This should help developers trying to either debug torch_mlir or use it
for the purpose of extracting MLIR outputs for other testing.

Fixes llvm#1175

Author: rengolin

development.md

@@ -120,6 +120,28 @@ cmake --build build
 export PYTHONPATH=`pwd`/build/tools/torch-mlir/python_packages/torch_mlir:`pwd`/examples
 ```
 
+## Testing MLIR output in various dialects
+
+To test the compiler's output to the different MLIR dialects, you can use the example `examples/torchscript_resnet18_all_output_types.py`.
+
+Make sure you have activated the virtualenv and set the `PYTHONPATH` above:
+```shell
+source mlir_venv/bin/activate
+export PYTHONPATH=`pwd`/build/tools/torch-mlir/python_packages/torch_mlir:`pwd`/examples
+python examples/torchscript_resnet18_all_output_types.py
+```
+
+This will display the Resnet18 network example in three dialects: TORCH, LINALG on TENSORS and TOSA.
+
+The main functionality is on `torch_mlir.compile()`'s `output_type`.
+
+Ex:
+```python
+module = torch_mlir.compile(resnet18, torch.ones(1, 3, 224, 224), output_type="torch")
+```
+
+Currently, `output_type` can be: `TORCH`, `TOSA`, `LINALG_ON_TENSORS`, `RAW` and `MHLO`.
+
 ## Jupyter
 
 Jupyter notebook: