Web Assets feature: Some way to set Headers for requests

[laundmo]

What problem does this solve or what need does it fill?

A common authentication scheme is providing Tokens/Keys as a Header. Similarily, some public services require, in their ToS/License, a custom User-Agent header for each application with some kind of identifiable information (email address of developer) they can use to reach out in case of (accidental) abuse.

What solution would you like?

My ideas:

• A pre-request callback which is passed the asset path (URL) and can return settings for that request (more flexible)
• A field on the plugin which allows customizing request settings like Headers per (sub-)domain

What alternative(s) have you considered?

Relying on third party libraries for this: Duplicates work and code to maintain

Additional context

There is a series of PRs for bevy_web_asset about this, partially by me, which never got merged.

• Add field for setting the user agent johanhelsing/bevy_web_asset#24
• Enable setting headers and query parameters. Also add 'fake extensions' mechanism. johanhelsing/bevy_web_asset#35 (mine)
• Switch to ureq, and store headers/query in a resource johanhelsing/bevy_web_asset#36 (mine)