readme: added env. variable to docker run command

README.md

@@ -24,13 +24,13 @@ docker build -t targettracking -f Dockerfile .
 #### Step 3
 Run the Docker image
 ```
-docker run --rm -it -p 8888:8888 targettracking
+docker run --rm -it -p 8888:8888 -e JUPYTER_LAB_ENABLE=yes targettracking
 ```
 This opens up a Jupyter lab instance on port 8888 which you can open in any browser.
 ### Alternative 2: Pull Docker image from Container Registry
 Run the Docker image (with notebooks) by running
 ```
-docker run --rm -it -p 8888:8888 gitlab.liu.se:5000/phd-courses/multiple-target-tracking
+docker run --rm -it -p 8888:8888 -e JUPYTER_LAB_ENABLE=yes gitlab.liu.se:5000/phd-courses/multiple-target-tracking
 ```
 
 # Documentation