fix(avro)!: support named type references (#32)

* feat: add Obfuscan workflow for pull requests

Adds a new job named Obfuscan to the CI workflow to scan the pull request diff using the ByteBardOrg/obfuscan-action.
This job runs only when a pull request is opened, and it uses the head SHA of the pull request to check for potential issues in the code changes before the main build proceeds.

* fix(avro)!: support named type references

Adds Avro-specific named type handling for schemas that reference previously defined records, enums, or fixed types by name.

Introduces `AvroNamedType`, keeps AsyncAPI `$ref` handling unchanged, supports recursive schemas like `LongList`, and widens map `values` to accept any Avro schema instead of only primitive types.

Existing construction with `AvroPrimitiveType` is preserved through the existing implicit conversion to `AsyncApiAvroSchema`, and primitive schema values can be converted back with an explicit cast.

BREAKING CHANGE: `AvroMap.Values` now uses `AsyncApiAvroSchema` instead of `AvroPrimitiveType`.

* refactor: error and warning collection in document reader

Changed how validation errors and warnings are added to the diagnostic collection. Previously, all items from the validation result were iterated over. This change explicitly separates the handling of AsyncApiValidatorError into diagnostic.Errors and AsyncApiValidatorWarning into diagnostic.Warnings, ensuring correct categorization of validation feedback.

* docs: add schema wiki page

* remove docs file

Author: VisualBean

src/ByteBard.AsyncAPI.Readers/AsyncApiJsonDocumentReader.cs

@@ -165,10 +165,15 @@ public T ReadFragment<T>(JsonNode input, AsyncApiVersion version, out AsyncApiDi
             if (this.settings.RuleSet != null && this.settings.RuleSet.Rules.Count > 0)
             {
                 var errors = element.Validate(this.settings.RuleSet);
-                foreach (var item in errors)
+                foreach (var item in errors.OfType<AsyncApiValidatorError>())
                 {
                     diagnostic.Errors.Add(item);
                 }
+
+                foreach (var item in errors.OfType<AsyncApiValidatorWarning>())
+                {
+                    diagnostic.Warnings.Add(item);
+                }
             }
 
             return (T)element;