Add indication of auto-generation to generated bindings

### Description

This is mainly for the C# bindings; warnings are reported in the file due to style inconsistencies. Of course, we can't (or shouldn't) edit `LiveSplitCore.cs` directly. To suppress warnings in the file, I suggest adding something like this to the generated file:

```cs
//---------------------------------------------------------------------------
//
// This code was generated by a tool.
// livesplit-core v0.13.0
//
// Changes to this file may cause incorrect behavior and will be lost if
// the code is regenerated.
//
//---------------------------------------------------------------------------
```
This is consistent with other .NET source code generators. The `` element suppresses all warnings.

Locate the generator that produces the C# bindings file LiveSplitCore.cs and inspect how its file header is assembled. Add the proposed auto-generated indication to the generated output, then verify that regeneration produces the marker and suppresses the reported warnings.

Written by the indexing model from the issue text.