fix: syntax highlighting lost when toggling Editable on MudCodeViewer

When the `Editable` parameter changes, syntax highlighting is lost
until the text is modified.

This happens because no parameter scope is registered for `Editable`,
so `ParameterChanged` is never invoked on change. As a result, the
`MudCode.highlight` JS function isn't called after the DOM updates,
leaving the code unhighlighted.

I ran into this in my project; it's also reported in #628.

The fix registers `Editable` in the parameter scope, the same way as
`Code`, `ShowLineNumbers`, etc. This ensures `ParameterChanged` fires
when `Editable` changes, triggering `MudCode.highlight` to re-highlight
the code after the DOM update.

Author: Damien Braillard

src/CodeBeam.MudBlazor.Extensions.Code/Components/MudCodeViewer.razor.cs

@@ -23,6 +23,7 @@ public partial class MudCodeViewer : MudComponentBase
     private readonly ParameterState<string?> _code;
     private readonly ParameterState<bool> _showLineNumbers;
     private readonly ParameterState<bool> _wrap;
+    private readonly ParameterState<bool> _editable;
     private readonly ParameterState<bool> _header;
     private readonly ParameterState<CodeLanguage> _language;
 
@@ -42,6 +43,9 @@ public MudCodeViewer()
         _wrap = registerScope.RegisterParameter<bool>(nameof(Wrap))
             .WithParameter(() => Wrap)
             .WithChangeHandler(ParameterChanged);
+        _editable = registerScope.RegisterParameter<bool>(nameof(Editable))
+            .WithParameter(() => Editable)
+            .WithChangeHandler(ParameterChanged);
         _header = registerScope.RegisterParameter<bool>(nameof(ShowHeader))
             .WithParameter(() => ShowHeader)
             .WithChangeHandler(ParameterChanged);