Add 'unknown' to type keywords (#24606)

src/services/utilities.ts

@@ -1196,6 +1196,7 @@ namespace ts {
         SyntaxKind.VoidKeyword,
         SyntaxKind.UndefinedKeyword,
         SyntaxKind.UniqueKeyword,
+        SyntaxKind.UnknownKeyword,
     ];
 
     export function isTypeKeyword(kind: SyntaxKind): boolean {

tests/cases/fourslash/completionsTypeKeywords.ts

@@ -1,7 +1,10 @@
 /// <reference path="fourslash.ts" />
 
+// @noLib: true
+
 ////type T = /**/
 
-goTo.marker();
-verify.completionListContains("undefined", "undefined", undefined, "keyword");
-verify.not.completionListContains("await");
+verify.completions({
+    marker: "",
+    exact: ["T", "null", "void", "any", "boolean", "keyof", "never", "number", "object", "string", "symbol", "undefined", "unique", "unknown"],
+});