Support schemes in text document content (#2000)

Author: dbaeumer

_specifications/lsp/3.18/workspace/textDocumentContent.md

@@ -36,9 +36,9 @@ _Server Capability_:
  */
 export type TextDocumentContentOptions = {
 	/**
-	 * The scheme for which the server provides content.
+	 * The schemes for which the server provides content.
 	 */
-	scheme: string;
+	schemes: string[];
 };
 ```