doc fixes

Author: CarloLucibello

README.md

@@ -15,10 +15,15 @@ Its most relevant features are:
 
 ## Installation
 
+GraphNeuralNetworks.jl is a registered julia package. 
+You can easily install it through the package manager:
+
 ```julia
-]add GraphNeuralNetworks
+julia> ]
+
+pkg> add GraphNeuralNetworks
 ```
 
 ## Usage
 
-Usage examples can be found in the [examples](https://github.com/CarloLucibello/GraphNeuralNetworks.jl/tree/master/examples) folder. 
+Usage examples can be found in the [examples](https://github.com/CarloLucibello/GraphNeuralNetworks.jl/tree/master/examples) folder. Also, make sure to read the [documentation](https://CarloLucibello.github.io/GraphNeuralNetworks.jl/dev) for a comprehensive introduction to the library.