mark the tutorial language as a LSP extension

Author: matthewbastien

Contributor Documentation/LSP Extensions.md

@@ -622,3 +622,10 @@ export interface GetReferenceDocumentResult {
   content: string;
 }
 ```
+
+## Languages
+
+Added a new language with the identifier `tutorial` to support the `*.tutorial` files that
+Swift DocC uses to define tutorials and tutorial overviews in its documentation catalogs.
+It is expected that editors send document events for `tutorial` and `markdown` files if
+they wish to request information about these files from SourceKit-LSP.

Sources/LanguageServerProtocol/SupportTypes/Language.swift

@@ -154,7 +154,7 @@ public extension Language {
   static let shellScript = Language(rawValue: "shellscript")  // Shell Script (Bash)
   static let sql = Language(rawValue: "sql")
   static let swift = Language(rawValue: "swift")
-  static let tutorial = Language(rawValue: "tutorial")
+  static let tutorial = Language(rawValue: "tutorial")  // LSP Extension: Swift DocC Tutorial
   static let typeScript = Language(rawValue: "typescript")
   static let typeScriptReact = Language(rawValue: "typescriptreact")  // TypeScript React
   static let tex = Language(rawValue: "tex")