sort: add -h option (#859)

per discussion in #588

pages/linux/sort.md

@@ -0,0 +1,19 @@
+# sort
+
+> Sort lines of text files.
+
+- Sort a file in ascending order:
+
+`sort {{filename}}`
+
+- Sort a file in descending order:
+
+`sort -r {{filename}}`
+
+- Sort the passwd file by the 3rd field, numerically:
+
+`sort -t: -k 3n /etc/passwd`
+
+- Sort human-readable numbers (in this case the 5th field of `ls -lh`):
+
+`ls -lh | sort -h -k 5`