Development of a Series of Biobased Poly(ethylene 2,5-furandicarboxylate-co-(5,5'-((phenethylazanediyl)bis(methylene))bis(furan-5,2-diyl))dimethylene 2,5-furandicarboxylate) Copolymers via a Sustainable and Mild Route: Promising “Breathing” Food Packaging Materials