docs: add further reading section for drivers

Signed-off-by: Justin Chadwell <me@jedevc.com>

docs/guides/drivers/docker-container.md

@@ -67,3 +67,9 @@ $ docker image ls
 REPOSITORY                       TAG               IMAGE ID       CREATED             SIZE
 <image>                          latest            adf3eec768a1   2 minutes ago       197MB
 ```
+
+## Further reading
+
+For more information on the docker-container driver, see the [buildx reference](https://docs.docker.com/engine/reference/commandline/buildx_create/#driver).
+
+<!--- FIXME: for 0.9, make reference link relative --->

docs/guides/drivers/kubernetes.md

@@ -230,3 +230,9 @@ $ docker buildx create \
 ```
 
 This will create your pods without `securityContext.privileged`.
+
+## Further reading
+
+For more information on the kubernetes driver, see the [buildx reference](https://docs.docker.com/engine/reference/commandline/buildx_create/#driver).
+
+<!--- FIXME: for 0.9, make reference link relative --->

docs/guides/drivers/remote.md

@@ -174,3 +174,5 @@ $ docker buildx create \
   --driver remote \
   kube-pod://buildkitd-XXXXXXXXXX-xxxxx
 ```
+
+<!--- FIXME: for 0.9, add further reading section with link to reference --->