md5: split basic example for simplicity, add example of md5 checksum for given string

pages/osx/md5.md

@@ -2,12 +2,19 @@
 
 > Calculate MD5 cryptographic checksums
 
-- Calculate the MD5 checksum for file(s) or files in a directory, one checksum per file
+- Print MD5 checksum for file
 
 `md5 {{filename1}}`
+
+- Print MD5 checksum for each file in a list or directory
+
 `md5 {{filename1}} {{filename2}}`
 `md5 {{directory/\*}}`
 
 - Output only the md5 checksum (no filename)
 
 `md5 -q {{filename}}`
+
+- Print a checksum of the given string
+
+`md5 -s {{string}}`