add missing copyright header

Author: matthewbastien

Diff for: Sources/DocCDocumentation/DocCDocumentationManager.swift

@@ -1,3 +1,15 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2025 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+//
+//===----------------------------------------------------------------------===//
+
 import BuildServerProtocol
 package import BuildSystemIntegration
 package import Foundation