Add rust & python examples

[yusefnapora]

While JS & Go are the immediate priority, we should also add rust and python examples as part of #29

As with JS and go, the ideal outcome is one where the example code live in its own repo (or the main libp2p repo for the language), and is covered by CI, etc. We should pull the narrative / explanation and format it for inclusion in the docs site, and also link to the source and build / run instructions.

The rust and python examples are currently light on framing / explanation, so adding some will be part of the work.

Here's the current examples (may need to revisit when we actually pick this up):

Rust:

• chat
• kad dht
• mDNS passive discovery

Python:

• chat

[p-shahi]

@DannyS03 plans to combine the Tutorials and Examples section in the future, so some of this work will be addressed by that.

[p-shahi]

closing #29 (comment)