Improve docker section in docs

docker/reference.md

@@ -1,23 +1,33 @@
-After running the tests with docker, you will need Docker installed and the docker image downloaded.
+# Testing with Docker
+
+Before running the tests with docker, you'll need Docker installed and the docker image downloaded.
 
 ## Install docker
-`sudo apt install docker.io && sudo usermod -aG docker $(whoami)`
+
+```shell
+$ sudo apt install docker.io && sudo usermod -aG docker $(whoami)
+```
 
 ## Download image
-`docker pull carto/IMAGE`
+
+```shell
+docker pull carto/IMAGE
+```
 
 ## Carto account
-https://hub.docker.com/r/carto/
+
+* `https://hub.docker.com/r/carto/`
 
 ## Update image
-- Edit the docker image file with your desired changes
-- Build image:
-  - `docker build -t carto/IMAGE -f docker/DOCKER_FILE docker/`
 
-- Upload to docker hub:
-  - Login into docker hub:
-    - `docker login`
-  - Create tag:
-    - `docker tag carto/IMAGE carto/IMAGE`
-  - Upload:
-    - `docker push carto/IMAGE`
+* Edit the docker image file with your desired changes
+* Build image:
+  * `docker build -t carto/IMAGE -f docker/DOCKER_FILE docker/`
+
+* Upload to docker hub:
+  * Login into docker hub:
+    * `docker login`
+  * Create tag:
+    * `docker tag carto/IMAGE carto/IMAGE`
+  * Upload:
+    * `docker push carto/IMAGE`