Add contend descriptor to code blocks

README.md

@@ -63,7 +63,7 @@ If you've created a production build (without `--build-arg NOFRONTEND=1`) you do
 The repository of a tutorial-framework based challenge is quite similar to a regular challenge.
 The project root should look something like this:
 
-```
+```text
 your_repo
 ├── solvable
 │   └── [TFW based Docker image]
@@ -82,7 +82,7 @@ From now on we are going to focus on the `solvable` image.
 
 Let us take a closer look on `solvable`:
 
-```
+```text
 solvable
 ├── Dockerfile
 ├── nginx        webserver configurations
@@ -104,7 +104,7 @@ This means that in order to listen on more than a single port we must use a reve
 Any `.conf` files in `solvable/nginx/` will be automatically included in the nginx configuration.
 In case you want serve a website or service you must proxy it through `TFW_PUBLIC_PORT`.
 This is really easy: just create a config file in `solvable/nginx/` similar to this one:
-```
+```text
 location /yoururl {
         proxy_pass http://127.0.0.1:3333;
 }
@@ -124,7 +124,7 @@ You can even configure your processes to start with the container by including `
 
 To run your own webservice for instance you need to create a config file in `solvable/supervisor/` similar to this one:
 
-```
+```text
 [program:yourprogram]
 user=user
 directory=/home/user/example/
@@ -151,7 +151,7 @@ If all you want to do is start a simple web application and send some messages y
 This folder contains the source code of a server running TFW and an other server running our event handlers.
 Note that this is not a part of the framework by any means, these are just simple examples.
 
-```
+```text
 solvable/src
 ├── tfw_server.py           tutorial-framework server
 ├── event_handler_main.py   event handlers implemented in python