Web IDL validation errors

[autokagami]

🤖 This is an automatic issue report for Web IDL validation error. 🤖

The bot found validation errors but couldn't fix them automatically, since the IDL texts include HTML tags. Please check the following messages and fix them.

• Validation error at line 2 in webcodecs,20, inside `interface Plane`:
  interface Plane {
            ^
  

  Error: Interfaces must have [Exposed] extended attribute. To fix, add, for example, [Exposed=Window]. Please also consider carefully if your interface should also be exposed in a Worker scope. Refer to the WebIDL spec section on Exposed for more information.

Please file an issue at https://github.com/saschanaz/webidl-updater/issues/new if you think this is invalid or should be enhanced.

[saschanaz]

Is there any good reason to have <xmp> inside <pre class='idl'>? I think they are redundant, no?