Add source-gen support for init and required members

Fix #114.

Author: xoofx

site/docs/serialization.md

@@ -256,6 +256,7 @@ public sealed class DatabaseConfig
 ```
 
 If `host` or `port` is missing from the TOML input, `TomlException` is thrown.
+Source-generated contexts also honor the C# `required` keyword and `init` accessors during deserialization.
 
 ### Example: constructor-based deserialization
 

site/docs/source-generation.md

@@ -36,6 +36,7 @@ internal partial class MyTomlContext : TomlSerializerContext { }
 The generator produces a `Default` singleton and a typed [`TomlTypeInfo<T>`](xref:Tomlyn.TomlTypeInfo`1) property for each root.
 Nested types referenced by the root are discovered transitively - you only need to annotate top-level types.
 Set [`TomlSerializableAttribute.TypeInfoPropertyName`](xref:Tomlyn.Serialization.TomlSerializableAttribute.TypeInfoPropertyName) when you want to customize the generated property name exposed by the context.
+Source-generated deserialization also supports C# `init` and `required` members.
 
 ## Use generated metadata