Add documentation, examples, and fix missing includes

Co-authored-by: johndoe6345789 <224850594+johndoe6345789@users.noreply.github.com>

src/backends/QemuBackend.cpp

@@ -1,5 +1,6 @@
 #include "backends/QemuBackend.h"
 #include <QProcess>
+#include <QDateTime>
 #include <QDebug>
 
 namespace gwt {

src/core/ArtifactManager.cpp

@@ -2,6 +2,7 @@
 #include "core/StorageProvider.h"
 #include <QDir>
 #include <QFile>
+#include <QFileInfo>
 #include <QDebug>
 
 namespace gwt {

src/core/RepoManager.cpp

@@ -2,6 +2,7 @@
 #include "core/StorageProvider.h"
 #include <QProcess>
 #include <QDir>
+#include <QFileInfo>
 #include <QDebug>
 
 namespace gwt {

src/core/StorageProvider.cpp

@@ -2,6 +2,8 @@
 #include <QStandardPaths>
 #include <QCryptographicHash>
 #include <QUrl>
+#include <QDir>
+#include <QFileInfo>
 #include <QDebug>
 
 namespace gwt {

src/gui/MainWindow.cpp

@@ -11,6 +11,7 @@
 #include <QInputDialog>
 #include <QMessageBox>
 #include <QLabel>
+#include <QFileInfo>
 
 namespace gwt {
 namespace gui {