update README.md

README.md

@@ -1,2 +1,29 @@
 # prettyjson
 prettyjson - command line JSON format tool.
+
+
+```
+$ prettyjson --help
+Usage:
+  prettyjson [OPTIONS] [FILE]
+
+prettyjson - command line JSON pretty tool.
+
+Positional arguments:
+  FILE                  FILE
+
+Optional arguments:
+  -h,--help             Show this help message and exit
+  -w,--tab-width TAB_WIDTH
+                        Tab width, default 4
+  -v,--version          Print version
+```
+
+```
+$ echo '{"k": "value"}' | prettyjson
+{
+    "k": "value"
+}
+```
+
+