Add literal operator to efficiently construct QString in Qt5

PR #16448.

src/base/global.h

@@ -48,3 +48,11 @@ constexpr typename std::add_const_t<T> asConst(T &&t) noexcept { return std::mov
 // Prevent const rvalue arguments
 template <typename T>
 void asConst(const T &&) = delete;
+
+#if (QT_VERSION < QT_VERSION_CHECK(6, 0, 0))
+// https://doc.qt.io/qt-6/qstring.html#operator-22-22_qs
+inline QString operator"" _qs(const char16_t *str, const std::size_t size)
+{
+    return QString::fromRawData(reinterpret_cast<const QChar *>(str), size);
+}
+#endif