LibWeb: Reset auto_placement_cursor_x after adding new column in GFC

We need to start looking from the beginning of current row if adding
new implicit column track made enough space to accomodate spanning item

This fixes placement for spanning grid items when `grid-auto-flow` is
specified to `column`.

Userland/Libraries/LibWeb/Layout/GridFormattingContext.cpp

@@ -606,6 +606,7 @@ void GridFormattingContext::place_item_with_no_declared_position(Box const& chil
                 auto_placement_cursor_y++;
             } else {
                 m_occupation_grid.set_max_column_index(auto_placement_cursor_x);
+                auto_placement_cursor_x = 0;
                 auto_placement_cursor_y = m_occupation_grid.min_row_index();
             }
         }