docs(discussion/04-server-vs-client.md): add headers

[gustavoguichard]

On lines 11-15 of this page, headers is listed along with loader and action so I thought it'd be cool to update the example to add a headers export. If that is not desirable, the headers item should probably removed from that list.

Also couple lil copy fixes

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[MichaelDeBoey]

Thanks for taking the time to create this PR @gustavoguichard! 🙏

However, I'm going to close this as the changes in here are already in #7191

[gustavoguichard]

Cool @MichaelDeBoey ! Appreciate the progress on the docs ;)