Add a data consent example

[dotproto]

Earlier this year Firefox announced plans to build data collection consent prompts into Firefox. Shortly thereafter it became available in Nightly for testing. As of November 3, AMO requires that new extensions use Firefox's built-in data collection consent APIs.

In order to help support developers attempting to adopt this API, we should add an example extension that demonstrates common usage patterns.

• Manifest: Use a mix of required and optional permissions
• Options page: Allow users to modify technical data grants
• Options page: Provide additional details about what data the extension transmits
• Options page: Allow users to uninstall the extension if they are not comfortable with required data transmission.
• Error reporting UI: Check for technical data permissions and, if they aren't grated, request permission in context.

[dotproto]

Tagged with needs info Needs more information to review or act on. as we should gather feedback from internal stakeholders on the design before proceeding.

[willdurand]

FWIW I do have an example at https://github.com/willdurand/example-extensions/tree/main/data-collection-with-fallback