Qt/FilesystemWidget: Add size column

Source/Core/DiscIO/Filesystem.cpp

@@ -8,6 +8,19 @@ namespace DiscIO
 {
 FileInfo::~FileInfo() = default;
 
+u64 FileInfo::GetTotalSize() const
+{
+  if (!IsDirectory())
+    return GetSize();
+
+  u64 size = 0;
+
+  for (const auto& entry : *this)
+    size += entry.GetTotalSize();
+
+  return size;
+}
+
 FileSystem::~FileSystem() = default;
 
-}  // namespace
+}  // namespace DiscIO