It feels like there is an easy footgun of implementing a unique event handler in some interface and forgetting to update the list.

We should be able to add a new entry to

that generates that list for us instead. We would need to:

1. Iterate over all descriptors
2. Ignore any descriptor without isInterface()
3. Iterate over descriptor.interface.members
4. Ignore any member that is not isAttr()
5. Ignore any member where member.type is not isInterface() or member.type.identifier.name is not EventHandler
6. Add member.identifier.name to the list of content event handlers

After all descriptors have been checked generate identical code to the hand-written code, and use the generated code from eventtarget.rs.

and are examples of how similar code generation is implemented.