Add types for String#isWellFormed and String#toWellFormed (#58010)

Co-authored-by: Nathan Shively-Sanders <293473+sandersn@users.noreply.github.com>

src/compiler/commandLineParser.ts

@@ -236,6 +236,7 @@ const libEntries: [string, string][] = [
     ["esnext.object", "lib.esnext.object.d.ts"],
     ["esnext.array", "lib.esnext.array.d.ts"],
     ["esnext.regexp", "lib.esnext.regexp.d.ts"],
+    ["esnext.string", "lib.esnext.string.d.ts"],
     ["decorators", "lib.decorators.d.ts"],
     ["decorators.legacy", "lib.decorators.legacy.d.ts"],
 ];