Make helia configurable using env vars.

[SgtPooki]

A few points of interest:

1. Kubo has experience with ENV_VARs and years of development that we can benefit from
2. Helia has no CLI (currently, empty repo exists at https://github.com/ipfs/helia-cli) so.. we don't have this yet.

A few potential paths forward

• We may just add ENV_VAR support to all config options directly in Helia
• May be useful to create a package @helia/env-vars-to-config type package that could be consumed by helia-cli or any other users of helia for populating their config, that consolidates all our environment variables

Env vars should be able to configure a few things:

• trustless gateway urls to use with blockBrokers
• libp2p transports?
• others

[SgtPooki]

marking this as done