Add overview of the Acoustic Representation Toolbox to the README

[aza]

I'd like to be able to link people to the https://github.com/earthspecies/representation-toolbox repo and have the ReadMe walk visitors through what the Acoustic Representation Toolbox is and why it matters, maybe with some examples, and also a description and exemplar for each of the types of representations. Audience is broader than just machine learners, can assume smart with some technical grasp. The overview should be broader and the examples of each type can be a little more technical.

https://github.com/earthspecies/representation-toolbox

[pcbermant]

Ok for sure! Last week, it said something like 'WIP' or 'This README will be updated shortly', but Katie (thankfully!) sent me a reminder to update it. It's still very much a WIP, and some modules are rougher than others (🙈) , but I can definitely work on expanding the README!