LibJS: Hook up the 'v' (unicodeSets) RegExp flag

Author: https://github.com/alimpfard
Commit: f4b26b0cea
Pull-request: https://github.com/SerenityOS/serenity/pull/14592
Reviewed-by: https://github.com/linusg ✅

Userland/Libraries/LibJS/Tests/builtins/RegExp/RegExp.prototype.flags.js

@@ -5,8 +5,11 @@ test("basic functionality", () => {
     expect(/foo/i.flags).toBe("i");
     expect(/foo/m.flags).toBe("m");
     expect(/foo/s.flags).toBe("s");
+    expect(/foo/v.flags).toBe("v");
     expect(/foo/u.flags).toBe("u");
     expect(/foo/y.flags).toBe("y");
     // prettier-ignore
     expect(/foo/dsgimyu.flags).toBe("dgimsuy");
+    // prettier-ignore
+    expect(/foo/dgimsvy.flags).toBe("dgimsvy");
 });