pubmodchap;pubmodcovr;pubmodcss;pubmodfont;pubmodimg;pubmodmath;pubmodsidx;/// Returns true if the tag is one of the known chunk types.
pubfnis_known_chunk(tag:&[u8; 4])->bool{matches!(
tag,b"CHAP"|b"IMG_"|b"CSS_"|b"FONT"|b"COVR"|b"COVT"|b"NOTE"|b"SIDX"|b"MATH")}