Add Batch Transactions tutorial

[maria-robobug]

The Batch amendment comes with a couple of terrific features, like the ability to provide atomic swaps with multiple signers involved for different Inner transactions inside one Batch. I absolutely love the things we can do with that feature. And I've been deep in code playing with these features. I have spent a significant amount of time by now to understand how this works on a signing, hashing and encoding level. What was striking is the complete lack of examples, resulting in the need to do a lot of searching/trying/reverse engineering (test cases) to be able to use it. Which is OK, it's a new feature, on devnet, and it's fine to accept that tutorials, sample code, etc. stil have to be created and published.

We should address the above feedback. The feature is available on Devnet, so we should be able to provide tutorials/examples to show developers how to use this.