Update docs to match readme (#104)

* Update docs to match readme

* Update docs/src/index.md

Author: raphaelsaavedra

docs/src/index.md

@@ -8,16 +8,28 @@ by D. Creal, S. J. Koopman, and A. Lucas.
 
 ## Installation
 
-This package is registered so you can `Pkg.add` it as follows:
+This package is registered so you can simply `add` it using Julia's `Pkg` manager:
 ```julia
 pkg> add ScoreDrivenModels
 ```
 
+## Citing the package
+
+If you use ScoreDrivenModels.jl in your work, we kindly ask you to cite the package [paper](https://arxiv.org/abs/2008.05506):
+
+    @misc{bodin2020scoredrivenmodelsjl,
+    title={ScoreDrivenModels.jl: a Julia Package for Generalized Autoregressive Score Models},
+    author={Guilherme Bodin and Raphael Saavedra and Cristiano Fernandes and Alexandre Street},
+    year={2020},
+    eprint={2008.05506}
+    }
+
+
 ## Contributing
 
 Contributions to this package are more than welcome, if you find a bug or have any suggestions 
 for the documentation please post it on the 
 [github issue tracker](https://github.com/LAMPSPUC/ScoreDrivenModels.jl/issues).
 
 When contributing please note that the package follows the 
-[JuMP style guide](https://www.juliaopt.org/JuMP.jl/stable/style/).
+[JuMP style guide](https://jump.dev/JuMP.jl/stable/style/index.html).