Add public init for Responses.Body.Input

Author: Recouse

Sources/OpenAI/Responses/ResponsesBody.swift

@@ -130,6 +130,11 @@ public extension Responses {
             /// Text, image, or audio input to the model, used to generate a response. Can also contain
             /// previous assistant responses.
             public let content: [Content]
+
+            public init(role: Role, content: [Content]) {
+                self.role = role
+                self.content = content
+            }
         }
     }
 }