By Alex Lauer A denim jacket is an absolute springtime essential, but not all denim jackets are created equal. Sure, we can appreciate the simplicity of a 100% blue jean construction, but if we had to choose one layer to rule them all, we’d choose something with more utility, something with a blanket lining … Something like the Wallace & Barnes Blanket-Lined Denim Jacket, which is currently 34% off at J.Crew. Not only does it pair a throwback silhouette with a warm, striped blanket interior, but it’s topped with a corduroy collar for extra style points, which will come in handy when you and al…