Update README

Author: pyropy

README.md

@@ -1,3 +1,7 @@
 # Bitstream Go
 
-Implementation of [bitstream protocol](https://robinlinus.com/bitstream.pdf) in Go.
+Implementation of [bitstream protocol](https://robinlinus.com/bitstream.pdf) in Go.
+
+# Example usage
+
+You can find an example of how to use this library in the [example](example) directory.

example/README.md

@@ -1 +1,11 @@
-## TODO: Add usage examples
+# Example usage
+
+### Encrypting the file
+```
+go run example/main.go -action=encrypt -in=bitcoin.pdf -out=bitcoin-enc.pdf -hash=00000000000000000000000000000000000000 -preimage=0000000000000000000000000000000000000000 
+```
+
+#### Decrypting the file
+```
+go run example/main.go -action=decrypt -in=bitcoin-enc.pdf -out=bitcoin-dec.pdf -hash=00000000000000000000000000000000000000 -preimage=0000000000000000000000000000000000000000 
+```