Update README.md

Author: lukrop

README.md

@@ -1,2 +1,21 @@
-# pass-file
-A pass extension for adding arbitary files to the password store. https://www.passwordstore.org/
+# pass file
+`pass file` is a extension for adding arbitary files to the [pass](https://www.passwordstore.org/) password store. Files will be encoded using `base64` before encryption.
+
+## Usage
+```
+Usage: pass file attach|retrieve pass-name [path]
+  attach|add: add new file to password store
+  retrieve|show|cat: retrieve file from password store and print it to stdout
+```
+
+## Example usage
+Storing a PNG picture and retrieving it.
+```
+pass file attach pics/secretpic mypicture.png
+pass file retrieve pics/secretpic > retrieved-picture.png
+```
+Alternativley you can also use shortcuts for `attach` and `retrieve`:
+```
+pass file add article my_super_secret_revelations.txt
+pass file cat article
+```