[feature] App-specific debug instruction

[chutten]

The book of Glean has instructions about how to manually debug instrumentation per platform... but it lacks in satisfying users looking for a guide for specific instructions for a specific app.

For example, the docs do not (and arguably should not) mention the Firefox iOS UI for setting debug tags, or Firefox Desktop's about:glean interface, etc.

I think the Glean Dictionary is probably the best place we have (and the best place we intend to have in at least the medium term) for such guides.

This feature request is for:

• A design of where in the Glean Dictionary this could live and how it could look (the app's top page? Above the fold? Text or images?)
• A process for adding and editing this information. (do we link to the editor like Gleannotations? Do we make this part of integrating your app with Glean? Do we have a lint on the dictionary's build to ensure every app has something?)
• Guides for debugging at least the handful of biggest projects, plus maybe default content (just link to the Book of Glean?) for the rest.