docs(selection): fix className documentation

[arikchakma]

Corrected the className documentation in the Selection extension:

• Fixed description from "The class that is applied to the focused element" to "The class that is applied to the current selection"
• Corrected default value from has-focus to selection
• Fixed configuration example to use Selection.configure() instead of Focus.configure()

Fixed the type autocomplete also here ueberdosis/tiptap#7018

[vercel]

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