Add Inference Example

[DimitrisMantas]

Issue

I think the documentation would greatly benefit a complete example on how to properly load a trained checkpoint, test, and finally use it for inference on a single image by splitting it into tiles.

There's already a gist on this #431, but it doesn’t really work anymore and is only relevant for GeoDatasets.

Fix

No response

### Tasks

[Geethen]

This would be a great addition. the example in the gist requires the image data (used for inference) to fit into memory. rasterio allows windowed writing and accommodates larger than memory datasets. Another useful addition would be able to take care of the tiling artefacts that occur when running inference on patches. A potential post-processing fix.