Export a few more types/classes from the mention package

[Cyperghost]

📝 Provide a description of the new feature

There are currently no exports for a few types and classes that can be used in other auto-completion features similar to the mention auto-completion.
These types/classes are interesting

MentionsView from "@ckeditor/ckeditor5-mention/src/ui/mentionsview";
MentionFeedObjectItem from "@ckeditor/ckeditor5-mention/src/mentionconfig";
MentionListItemView from "@ckeditor/ckeditor5-mention/src/ui/mentionlistitemview";
DomWrapperView from "@ckeditor/ckeditor5-mention/src/ui/domwrapperview";

What is the expected behavior of the proposed feature?
We would use this to create our own auto-completion for others, then mention, but not completely rewrite everything.

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If you'd like to see this feature implemented, add a 👍 reaction to this post.

[Witoso]

Thanks for the request! @arkflpc @filipsobol , I'm not sure if we need to investigate this further, or just add it?

[filipsobol]

I'm not too familiar with this feature, so I can't make the final call, but in general I see no reason why we shouldn't do this.