Fix install code block

Author: ismael-lajaaiti

docs/src/index.md

@@ -9,11 +9,10 @@ Direct integration with [`EcologicalNetworksDynamics`](https://github.com/econet
 Install with
 
 ```julia
-using Pkg; Pkg.add(url = "https://github.com/econetoolbox/EcoNetPlot.jl");
-```
-```
+using Pkg; Pkg.add(url = "https://github.com/econetoolbox/EcoNetPlot.jl")
 ```
 
+
 ### Plotting from an adjacency matrix
 
 You have an adjacency matrix which represents an ecological networks, say, a food web.