docs: complete readme

README.md

@@ -2,7 +2,11 @@
 
 [![ci](https://github.com/chiefbiiko/gnark-witnejs/workflows/ci/badge.svg)](https://github.com/chiefbiiko/gnark-witnejs/actions/workflows/ci.yml)
 
-[gnark](https://github.com/Consensys/gnark) witness serializer in js.
+[gnark](https://github.com/Consensys/gnark) witness serializer in js
+
+```
+npm i gnark-witnejs
+```
 
 ## Usage
 
@@ -11,13 +15,12 @@ import serialize from "gnark-witnejs"
 
 const inputs = { x: 3n, y: 35n, z: [ [ 0n, 99n ], 77n ] }
 const publics = { x: true } // indicates public inputs
-const opts = {/* prime: BN254, publicOnly: false */}
+const opts = {/* modulus: BN254_R, publicOnly: false */}
 
 const buf = serialize(inputs, publics, opts)
 ```
 
 Make sure that:
-
++ input fields appear in the same order as in the golang struct
 + the input object does not contain nested objects
   > nested arrays are supported though
-+ input fields must appear in the same order as in the golang struct