Add an example to the README

Include a simple example and output plot so that the README is a bit
more exciting.

README.md

@@ -23,6 +23,30 @@ We take care of reading the metadata from the `*_MTL.txt` files provided by
 EarthExplorer and organizing the bands into a single data structure for easier
 manipulation, processing, and visualization.
 
+## Example
+
+Here's a quick example of loading this [Landsat 8 scene from the Brumadinho
+tailings dam disaster in Brazil](https://doi.org/10.6084/m9.figshare.21665630.v1):
+
+```python
+import xlandsat as xls
+import pooch  # for downloading the sample scene
+
+# Download the scene as a tar archive
+path = pooch.retrieve(
+      "doi:10.6084/m9.figshare.21665630.v1/cropped-after.tar.gz",
+     known_hash="md5:4ae61a2d7a8b853c727c0c433680cece",
+)
+# Load the scene directly from the archive (no need to unpack it)
+scene = xls.load_scene(path)
+# Make an RGB composite and add it to the scene Dataset
+scene = scene.assign(rgb=xls.composite(scene, rescale_to=[0, 0.2]))
+# Plot the composite
+scene.rgb.plot.imshow()
+```
+
+![RGB map showing the flooded plain after the dam collapse as light brown.]( https://raw.githubusercontent.com/compgeolab/xlandsat/main/doc/_static/readme-example.jpg)
+
 ## Project goals
 
 * Loading single scenes in the EarthExplorer format.