Make a list of major stakeholders/users to notify

[Hexcles]

In the wake of #40 (comment) (no one recalled Bikeshed used the manifest, too), I think we should document some institutional knowledge, namely a list of major stakeholders/users of various components so that we can notify them of potential breaking changes.

[jgraham]

I would suggest a infra-owners group who could be @-notified for RFCs changing data formats.

[Hexcles]

That's a good idea for large-scale changes. We probably also want a more detailed list somewhere, too, something like https://web-platform-tests.org/admin/index.html