Add help flag -h

lincache.sh

@@ -1,7 +1,6 @@
 #!/bin/sh -e
 # TODO: try to get lang from the original document since we download it anyway
 # TODO: switch for not downloading the original too
-# TODO: switch for custom language
 # TODO: support multiple URLs in one command
 # TODO: optionally minify HTML
 # TODO: download required resources too - images...
@@ -34,6 +33,10 @@ while true; do
             shift
             shift
             ;;
+        -h)
+            usage
+            exit 0
+            ;;
         *)
             url="$1"
             break