Without this macro, if any signals or slots were attempted to be used,
they wouldn't work; neither would various other features of the Qt
meta-object system. This can also lead to weird behavior in other
circumstances. Qt's documentation specifically states:
"Therefore, we strongly recommend that all subclasses of QObject use the
Q_OBJECT macro regardless of whether or not they actually use signals,
slots, and properties."
on its page for "The Meta-Object System", which can be seen here:
https://doc.qt.io/qt-5/metaobjects.html
Let's opt for "always do the right thing", and keep the code extensible
for the future and not have random things blow up on us.
