Editorial: Align with Web IDL specification

[autokagami]

🤖 This is an automated pull request to align the spec with the latest Web IDL specification. 🤖

The followings are the Web IDL validation messages, which may help understanding this PR:

• Validation error at line 4 in test-spec,0:
          void doTheFoo();
          ^
  

  Error: void is now replaced by undefined. Refer to the relevant GitHub issue for more information.

• Validation error at line 3 in test-spec,1:
          void doTheFoo();
          ^
  

  Error: void is now replaced by undefined. Refer to the relevant GitHub issue for more information.

• Validation error at line 6 in test-spec,1, inside `interface mixin MyMixin`:
          void doTheFoo(DOMString foo)
               ^
  

  Error: The operation "doTheFoo" has already been defined for the base interface "BaseInterface" either in itself or in a mixin

• Validation error at line 6 in test-spec,1:
          void doTheFoo(DOMString foo
          ^
  

  Error: void is now replaced by undefined. Refer to the relevant GitHub issue for more information.

• Validation error at line 1 in test-spec,2, inside `interface IHaveConstructor`:
        [Exposed=Window, Constructor] // cause merge conflict 7
                         ^
  

  Error: Constructors should now be represented as a constructor() operation on the interface instead of [Constructor] extended attribute. Refer to the WebIDL spec section on constructor operations for more information.

• Validation error at line 4 in test-spec,2:
          void doTheFoo();
          ^
  

  Error: void is now replaced by undefined. Refer to the relevant GitHub issue for more information.

• Validation error at line 1 in test-spec,3, inside `interface ImplicitlyExposed`:
        interface ImplicitlyExposed {
                  ^
  

  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.

• Validation error at line 3 in test-spec,3:
          void doTheFoo();
          ^
  

  Error: void is now replaced by undefined. Refer to the relevant GitHub issue for more information.

• Validation error at line 4 in test-spec,4, inside `interface IUseTheDictionary`:
        interface IUseTheDictionary {
                  ^
  

  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.

• Validation error at line 5 in test-spec,4:
          void doTheFoo(MyDictionary dict
          ^
  

  Error: void is now replaced by undefined. Refer to the relevant GitHub issue for more information.

• Validation error at line 5 in test-spec,4, inside `interface IUseTheDictionary -> operation doTheFoo -> argument dict`:
          void doTheFoo(MyDictionary dict);
                                     ^
  

  Error: Dictionary argument must be optional if it has no required fields

• Validation error at line 4 in test-spec,5:
          void doTheFoo(optional MyUnion
          ^
  

  Error: void is now replaced by undefined. Refer to the relevant GitHub issue for more information.

• Validation error at line 4 in test-spec,5:
          void doTheFoo(optional MyUnion? dict);
                                 ^
  

  Error: Nullable union cannot include a dictionary type.

• Validation error at line 4 in test-spec,5, inside `interface IAlsoUseTheDictionary -> operation doTheFoo -> argument dict`:
   doTheFoo(optional MyUnion? dict);
                              ^
  

  Error: Dictionary arguments cannot be nullable.

• Validation error at line 6 in test-spec,0, inside `dictionary Duplicated`:
        dictionary Duplicated {};
                   ^
  

  Error: The name "Duplicated" of type "interface" was already seen

Currently this autofix might introduce awkward code formatting, and feel free to manually fix it whenever it happens.

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