We have nothing for gathering browser exceptions in customer environments

Created by: slimsag

Today, when in-browser JS errors/exceptions occur, we have no way to identify them. We don't have anything gathering them, nothing reporting them to the users or site admins, and no way to easily ask users if they are occurring.

To see how painful this can make debugging some issues, see https://github.com/sourcegraph/infrastructure/issues/1514

When a user runs into a problem and a JS exception is occurring and we don't know about it, what is our plan to debug those problems?