fix(codegen): Adds access modifiers to serializable fields (#633)

- [X] Adds options for SerializableField.

Example:
```cs
[SerializableField(0, getter: "protected", setter: "protected", isVritual: true)]
private int _someField;
```

Defaults: `getter: "public", setter: "public", isVirtual: false`

Projects/SerializationGenerator/SourceGeneration/SourceGeneration.Namespace.cs

@@ -15,7 +15,7 @@
 
 using System.Text;
 
-namespace SourceGeneration
+namespace SerializationGenerator
 {
     public static partial class SourceGeneration
     {