Write a bitswap plugin for k6

# What

To enable bitswap load testing, let's setup K6 to execute bitswap requests via a javascript plugin

Docs on plugin writing:
https://k6.io/docs/extensions/get-started/create/javascript-extensions/#advanced-module-api

HTTP plugin source code:
https://github.com/grafana/k6/tree/master/js/modules/k6/http

# Suggested Implementation

- Spin up a libp2p node w/ go-bitswap
- For the API take a multiaddr + peerID + CID
- Add the peer ID + multiaddr to the swarm
- request a block from bitswap
- Remove the peer ID from the swarm

# Out of scope

DAG Walking, for now

# Acceptance criteria

We can write a script that fetches a Bitswap Block