Merge pull request scaleway#70 from sieben/add_documentation

Add documentation about volumes usage

website/docs/index.html.markdown

@@ -24,7 +24,7 @@ Here is an example that will setup the following:
 ```hcl
 provider "scaleway" {
   organization = "<YOUR-ACCESS-KEY>"
-  token        = "<YOUR-GENERATED-TOKEN>"
+  token        = "<YOUR-GENERATED-TOKEN>"
   region       = "par1"
 }
 
@@ -99,3 +99,12 @@ provider "scaleway" {
 - **SCALEWAY_ORGANIZATION**: Your Scaleway `organization` access key
 - **SCALEWAY_TOKEN**: Your API access `token`, generated by you
 - **SCALEWAY_REGION**: The Scaleway region
+
+## Volume usage
+
+You can add volumes to baremetal instances.
+The minimal size of increment is 50GB and you can add at most 15 different volumes on an instance.
+
+Additional volumes cannot be added to virtual cloud servers.
+
+Check out the list of different instances on the [pricing page](https://www.scaleway.com/pricing).