Synthesis, Structure, and Characterization of 4,4′-(Anthracene-9,10-diylbis(ethyne-2,1-diyl))bis(1-methyl-1-pyridinium) Bismuth Iodide (C₃₀H₂₂N₂)₃Bi₄I₁₈, an Air, Water, and Thermally Stable 0D Hybrid Perovskite with High Photoluminescence Efficiency