Update cheatsheets

tldr/b2sum

@@ -20,7 +20,7 @@ source: https://github.com/tldr-pages/tldr.git
 
 `{{command}} | b2sum`
 
-- Read a file of BLAKE2 sums and filenames and verify all files have matching checksums:
+- Read a file of BLAKE2 checksums and filenames and verify all files have matching checksums:
 
 `b2sum --check {{path/to/file.b2}}`
 
@@ -31,3 +31,7 @@ source: https://github.com/tldr-pages/tldr.git
 - Only show a message when verification fails, ignoring missing files:
 
 `b2sum --ignore-missing --check --quiet {{path/to/file.b2}}`
+
+- Check a known BLAKE2 checksum of a file:
+
+`echo {{known_blake2_checksum_of_the_file}} {{path/to/file}} | b2sum --check`