Feature Request: Add language designator for code sample shortcut in editor

When communicating with a mentor/student, when you click the code button it inserts the following template:

````
```
code text here
```
````

Unfortunately this doesn't include the color coding for the language syntax. Since we already know which language track the message refers to, it would be really cool if the template included the language signifier to add the appropriate code coloring. So if we're on the JavaScript track, it would be like this instead (by default):

````
```js
code text here
```
````

Start in the main Exercism repository by finding the editor's code-button shortcut and the entry point that knows the message's language track. Confirm how the current template is generated, then verify that clicking the button produces a language-tagged fenced block matching the active track.

Written by the indexing model from the issue text.