docs: fix markdown errors and update

project-docs/DOCKER_CHEAT_SHEET.md

@@ -2,7 +2,7 @@
 
 ## List running containers
 
-```
+```shell
 docker ps
 ```
 
@@ -10,7 +10,7 @@ docker ps
 
 In the directory of the `docker-compose.yml`:
 
-```
+```shell
 docker-compose ps
 ```
 
@@ -18,7 +18,7 @@ docker-compose ps
 
 `$CONTAINERID` from `docker ps`.
 
-```
+```shell
 docker restart $CONTAINERID
 ```
 
@@ -26,7 +26,7 @@ docker restart $CONTAINERID
 
 `$PROGRAM` can be any program that is installed in the container `bash`, `sh`, `node`, `curl`...
 
-```
+```shell
 docker exec -it $CONTAINERID $PROGRAM
 ```
 
@@ -34,7 +34,7 @@ docker exec -it $CONTAINERID $PROGRAM
 
 This removes unused images, networks, ... from your system.
 
-```
+```shell
 docker system prune
 ```