While Qt Designer doesn't care about casing, the XML schema spec does.
Due to Qt Creator automatically changing case on save, require the
uppercase variant in all situations, so that other devs don't have to
manually change the case after Qt Creator changes it.
NOTE: This introduces an adjustment to the spec, different from what
Qt provide from Qt Designer. If this file is changed in future, this
diff may need to be manually re-applied.
https://doc.qt.io/qt-5/designer-ui-file-format.html
As all the .ui files follow a set schema, providing a way to validate
that schema is useful for manual XML modifications.
XML-Schema-Qt5.15.xsd source: https://doc.qt.io/qt-5/designer-ui-file-format.html
Note: some lines had to be commented out as they are not valid in XSD.
When a new version of Qt is used, compare the diff and update as necessary.
This file doesn't do anything on its own, but can be paired with an IDE
or a standalone linter to perform validation.
