Harper could have support for QT Creator

QT Creator is an IDE for Qt and KDE

It could have a Harper extension either via [its extension API](https://doc.qt.io/qtcreator-extending/creating-plugins.html) or `harper-ls`

It wouldn't have to be part of the Harper project. It could be independent or part of the QT Creator project.

This would be a good first issue for somebody who already knows QT Creator.

There is even a [spellchecker plugin](https://github.com/CJCombrink/SpellChecker-Plugin) for it that ought to be a good basis.

Start by reviewing Qt Creator's extension API and the linked SpellChecker-Plugin, then compare that approach with integrating harper-ls. Done means a working Qt Creator integration exists, either in Harper or independently, with its location and setup documented.

Written by the indexing model from the issue text.