Allow to disable code block language highlighting on Markdown mode

### Describe the feature

Hi, first of all, thanks for your work here!.

Is there a way to disable code block highlighting for the `Markdown` mode?

For example:

```
.```javascript
let someVar;
.```
```

That will appear highlighted, and I would like to disable it.

### Use Case

There's no support for many languages so it is not consistent, which makes it look ugly. Disabling it should be an option.

### Proposed Solution

_No response_

### Other Information

_No response_

### Acknowledgements

- [ ] This feature might incur a breaking change
- [ ] I may be able to implement this feature request

### ACE version used

1.43.6