Set up docs testing folder to house code / snippets for reference by the docs

[critesjosh]

Create a folder for tests that are specific to the documentation.

The existing e2e tests are meant to test the protocol functionality and are not optimally designed or set up for educational or demonstration purposes. Having dedicated tests for the documentation to reference will help make the examples and tutorials in the docs more clear.

There is also the benefit that if any of the tests in this folder need to be changed, the dev rel team will be notified and can assess if any of the surrounding relevant documentation needs to be changed.

[critesjosh]

@sklppy88 i know we discussed using aztec-examples as a folder in aztec-packages for this, but i fear that it will quickly become overloaded with docs specific tests / snippets that aren't good standalone examples. I think it makes sense to start with a specific place for docs tests / snippets.

We can still do the thing where aztec-examples is in aztec-packages and is mirrored out, but I think it should be a distinct thing from the docs tests / snippets.