Rollup: Added constant RGB5_A1. (#23328)

utils/build/rollup.config.js

@@ -92,6 +92,7 @@ export function glconstants() {
 		POLYGON_OFFSET_FILL: 32823,
 		RGB8: 32849,
 		RGBA4: 32854,
+		RGB5_A1: 32855,
 		RGBA8: 32856,
 		TEXTURE_3D: 32879,
 		CLAMP_TO_EDGE: 33071,