[uievents] Please mark some definitions as not exported (#6)

I added UI Events to Shepherd's linking database yesterday, and now we're running into problems due to it using `<dfn>` for a bunch of terms that it's actually just referencing from other specs.

The best solution, of course, is switching to a preprocessor that does cross-spec linking, but in the meantime there's an easy fix - just mark them all as not exported!

In particular, please add a `data-no-export` boolean attribute to:
* The two `*Error` definitions in 3.6
* The list of IDL definitions in 4.0. (You can put it on the list element, as it's a container for all of them.)

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Reply to this email directly or view it on GitHub:
https://github.com/w3c/uievents/issues/6