style: add Hdlc to spell-checker ignore list

Fix cspell warning for Crc32IsoHdlc by adding Hdlc to the
spell-checker:ignore comment. Hdlc is a legitimate acronym
for High-Level Data Link Control used in CRC algorithms.

Author: naoNao89

src/uucore/src/lib/features/sum.rs

@@ -3,7 +3,7 @@
 // For the full copyright and license information, please view the LICENSE
 // file that was distributed with this source code.
 
-// spell-checker:ignore memmem algo PCLMULQDQ refin xorout
+// spell-checker:ignore memmem algo PCLMULQDQ refin xorout Hdlc
 
 //! Implementations of digest functions, like md5 and sha1.
 //!