Update emacs dependency to 26.1 for `seq-sort-by` usage.

xwidget-plus.el

@@ -5,7 +5,7 @@
 ;; Created: 2020-03-11
 ;; Keywords: convenience
 ;; Version: 0.1
-;; Package-Requires: ((emacs "25.3"))
+;; Package-Requires: ((emacs "26.1"))
 
 ;; This file is NOT part of GNU Emacs.