Misc: Add copyright/license statement to applicable files

Should've did this in the beginning.

src/duckstation-qt/memoryviewwidget.cpp

@@ -38,11 +38,7 @@ int MemoryViewWidget::asciiWidth() const
 void MemoryViewWidget::updateMetrics()
 {
   const QFontMetrics fm(fontMetrics());
-#if QT_VERSION >= QT_VERSION_CHECK(5, 11, 0)
   m_char_width = fm.horizontalAdvance(QChar('0'));
-#else
-  m_char_width = fm.boundingRect(QChar('0')).width();
-#endif
   m_char_height = fm.height();
 }