fix: address markdownlint errors

docs/install-understack-ubuntu-k3s.md

@@ -11,13 +11,15 @@ git clone https://github.com/rackerlabs/understack.git
 ## Install Pre-requisites
 
 Install some packages we'll need later and some useful troubleshooting utilities.
+
 ```bash
 apt-get -y install curl jq net-tools telnet git apt-transport-https wget
 ```
 
 ## Update Ubuntu
 
 Update to the latest ubuntu packages and reboot if necessary.
+
 ```bash
 apt-get -y update
 ```
@@ -90,13 +92,15 @@ K3s installer should give us a working kubernetes.
 The kubectl config from k3s is in `/etc/rancher/k3s/k3s.yaml` and kubectl will automatically use it.
 
 See everything running in the new k3s kubernetes cluster:
+
 ```bash
 kubectl get all --all-namespaces
 ```
 
 ## Install UnderStack
 
 Get the repo:
+
 ```bash
 git clone https://github.com/rackerlabs/understack.git
 ```
@@ -108,6 +112,7 @@ References:
 ### Bootstrap UnderStack
 
 Run the initial bootstrap:
+
 ```bash
 kubectl kustomize --enable-helm bootstrap | kubectl apply --server-side -f -
 ```