docs: Example for customizing fetch requests to trustless gateways

[Dhruv-Varshney-developer]

Title

docs: Example for customizing fetch requests to trustless gateways

Description

Add example code to the packages/block-brokers/README.md demonstrating how to customize the fetch requests sent to trustless gateways using the transformRequestInit option.This shows how to add authentication headers (such as JWT tokens) when using the TrustlessGatewayBlockBroker.

Completes #757 .

Notes & open questions

Change checklist

• I have performed a self-review of my own code
• I have made corresponding changes to the documentation if necessary (this includes comments as well)
• I have added tests that prove my fix is effective or that my feature works

[2color]

Please move the example to index.ts of the package, because the README file is generated automatically from it, and will be overwritten in the build.

For example, for the dag-json package, this is the source:

helia/packages/dag-json/src/index.ts

Lines 1 to 26 in 7e32123

	/**
	* @packageDocumentation
	*
	* `@helia/dag-json` makes working with DAG-JSON {@link https://github.com/ipfs/helia Helia} simple & straightforward.
	*
	* See the {@link DAGJSON} interface for all available operations.
	*
	* @example
	*
	* ```typescript
	* import { createHelia } from 'helia'
	* import { dagJson } from '@helia/dag-json'
	* import { CID } from 'multiformats/cid'
	*
	* const helia = await createHelia()
	* const j = dagJson(helia)
	*
	* const cid = await j.add({
	* hello: 'world'
	* })
	* const obj = await j.get(cid)
	*
	* console.info(obj)
	* // { hello: 'world' }
	* ```
	*/

• Make sure the style is consistent by using npx aegir lint and npx aegir lint -- --fix
• To generate the readme run npx aegir docs

Also left some comments in line.

[Dhruv-Varshney-developer]

Hi @2color,
I have made all the changes as suggested, including moving the example to index.ts, ensuring the README is generated correctly, and following the required styles with npx aegir lint --fix.

I’ve also added the example for createHelia({ blockBrokers: [...] }) as requested. Let me know if any more improvements are needed!

[Dhruv-Varshney-developer]

Hi @2color ,
It would be helpful if you could review and merge it. Let me know if any improvements are needed from my end.
Thanks for your work!

[Dhruv-Varshney-developer]

Hi @2color,
Is there something that needs improvement here?

[Dhruv-Varshney-developer]

Hi @2color @SgtPooki ,
I have addressed all the requested changes:

• Fixed the .cat() issue
• Removed log statements
• Updated labels - Applied appropriate labeling as requested
• Generated documentation - README now reflects the corrected example

You can verify the working example at: https://github.com/Dhruv-Varshney-developer/test-example-helia

I've also updated the CID in the example to use bafkreife2klsil6kaxqhvmhgldpsvk5yutzm4i5bgjoq6fydefwtihnesa (contains "hello world") from the IPFS documentation to ensure the example works reliably for users.

The PR is now ready for review.
Please let me know if any additional improvements are needed.
Thanks!