Add reference to blogs in documentation

[mnaser]

We've got some awesome community members who have pushed up blogs regarding how to use CAPI,

• https://satishdotpatel.github.io/openstack-magnum-capi/
• https://satishdotpatel.github.io/kubernetes-cluster-autoscaler-with-magnum-capi/
• https://www.roksblog.de/openstack-magnum-cluster-api-driver/

We should add these as a "References" section, with a link to the Article and their author to give them exposure.