Add source generator

Auto assign defined fields to name of field and incremental value start from 1
class must be defined as partial with Attribute [SmartEnumGenerator] and all fields must be static

example class with SmartEnumGenerator and no inheritance from SmartEnum
```csharp
[SmartEnumGenerator]
public sealed partial class Permissions
{
public static readonly Permissions Dashboard;
public static readonly Permissions UserManagement;
}
```
generated code will be
```csharp
namespace SmartEnum.SourceGenerator.UnitTests
{
public sealed partial class Permissions : SmartEnum
{
public Permissions(string name, int value) : base(name, value) {}

static Permissions()
{
Dashboard = new Permissions(nameof(Dashboard), 1);
UserManagement = new Permissions(nameof(UserManagement), 2);
}
}
}
```

example class with SmartEnumGenerator and inheritanced from SmartEnum
```csharp
namespace SmartEnum.SourceGenerator.UnitTests
{
[SmartEnumGenerator]
public sealed partial class Subscriptions : SmartEnum
{
public static readonly Subscriptions Free;
public static readonly Subscriptions Sliver;
public static readonly Subscriptions Gold;

public Subscriptions(string name, int value) : base(name, value)
{
}
}
}

```
generated code will be
```csharp
namespace SmartEnum.SourceGenerator.UnitTests

{
public sealed partial class Subscriptions
{
static Subscriptions()
{
Free = new Subscriptions(nameof(Free), 1);
Sliver = new Subscriptions(nameof(Sliver), 2);
Gold = new Subscriptions(nameof(Gold), 3);
}
}
}

```

Note: //in future we can define a custom attribute to ignore field
I'll do a pull request for this feature in separated package called SmartEnum.SourceGenerator

Start with the issue's two C# examples and compare the requested generated output for inherited and non-inherited classes. Define completion as a separate SmartEnum.SourceGenerator package that generates the shown constructors, static initialization, names, and values, with tests covering both examples.

Written by the indexing model from the issue text.