Use icon from qrc for system tray icon

Fixes the system tray on Windows

res.qrc

@@ -1,5 +1,6 @@
 <RCC>
     <qresource prefix="/">
+        <file alias="icons/org.kde.neochat.svg">org.kde.neochat.svg</file>
         <file>qml/main.qml</file>
         <file>imports/NeoChat/Page/qmldir</file>
         <file>imports/NeoChat/Page/LoadingPage.qml</file>

src/trayicon.cpp

@@ -12,7 +12,7 @@
 TrayIcon::TrayIcon(QObject *parent)
     : QSystemTrayIcon(parent)
 {
-    setIcon(QIcon::fromTheme("org.kde.neochat"));
+    setIcon(QIcon(":/icons/org.kde.neochat.svg"));
     QMenu *menu = new QMenu();
     auto viewAction_ = new QAction(i18n("Show"), parent);