feat(cbindings): tiny waku relay example in Python

[Ivansete-status]

Description

Nwaku integration library (libwaku.so) in Python

Changes

• Adding new waku.py that shows an example on how to integrate nwaku (libwaku.so) in Python.
• libwaku.nim: adapting code to latest changes made in 34a9263

How to test

1. Open a terminal in the root folder and run the next (python3 should be installed beforehand:)

   python3 examples/python/waku.py -p 60000 -k 364d111d729a6eb6d2e6113e163f017b5ef03a6f94c9b5b7bb1bb36fa5cb07a9 -r 1
   

2. Open a second terminal window and run the next from within the repo's root folder:

   ./build/wakunode2 --config-file=cfg_node_b.txt
   

   cfg_node_b.txt
3. Open a third terminal and run:

   while [ true ]; do curl -d "{\"jsonrpc\":\"2.0\",\"id\":"$(date +%s)",\"method\":\"post_waku_v2_relay_v1_message\", \"params\":[\"/waku/2/default-waku/proto\", {\"timestamp\":"$(date +%s)", \"payload\":\"VGhpcyBpcyBhIG1lc3NhZ2UK\"}]}" --header "Content-Type: application/json" http://localhost:8546; done
   

At this stage, in the first terminal (python) there should appear sth like:
Event received: b'{"pubsubTopic":"/waku/2/default-waku/proto","messageId":"TODO","wakuMessage":{"payload":"This is a message\\n","contentTopic":"/waku/2/default-content/proto","version":0,"timestamp":1686582003},"eventType":"message"}'

Issue

#1632

[rymnc]

LGTM

[jm-clius]

Thanks for this!