Properly stylize the application name (#3775)

This is just a cosmetic change. On KDE Plasma, the title of the tray icon is set by either the name of the binary, or by calling `setApplicationName()`. So having it properly stylized looks better.

src/main.cpp

@@ -60,7 +60,7 @@ int main(int argc, char** argv)
 #endif
 
     Application app(argc, argv);
-    Application::setApplicationName("keepassxc");
+    Application::setApplicationName("KeePassXC");
     Application::setApplicationVersion(KEEPASSXC_VERSION);
     // don't set organizationName as that changes the return value of
     // QStandardPaths::writableLocation(QDesktopServices::DataLocation)