sha*sum: add example about the creation of a list of checksums

pages/common/shasum.md

@@ -14,6 +14,10 @@
 
 `shasum --algorithm 512 {{filename1}} {{filename2}}`
 
+- Calculate and save the list of SHA256 checksums to a file
+
+`shasum --algorithm 256 {{filename1}} {{filename2}} > {{filename.sha256}}`
+
 - Check a file with a list of sums against the directory's files:
 
 `shasum --check {{list_file}}`