Adding Example/Tutorial of importing data to Xarray (Merge/conact/etc)

I love xarray for analysis but getting my data into xarray often takes a lot more time than I think it should. I am a hydrologist and very often hydro data is poorly stored/formatted, which means I need to do multiple merge/conact/combine_first operations etc. to get to a nice xarray dataset format. I think having more examples for importing different types of data would be helpful (for me and possibly others), instead of my current approach, which often entails trial and error.

I can start off by providing an example of importing funky hydrology data that hopefully would be general enough for others to use. Maybe we can compile other examples as well. With the end goal of adding to the readthedocs.

@klapo @jhamman