Implement Ctrl+S or Command+S for save draft (#1628)

* Implement Ctrl+S or Command+S for save draft

* rename

* add Typecho.savePost

* fix upload file size

* add new uploader

* replace new uploader

* fix textarea change

* fix preview

* refactor post edit

* fix issue

* fix page edit

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Co-authored-by: joyqi <joyqi@segmentfault.com>
Co-authored-by: joyqi <magike.net@gmail.com>

admin/backup.php

@@ -84,6 +84,7 @@ $backupFiles = \Widget\Backup::alloc()->listFiles();
 <?php
 include 'copyright.php';
 include 'common-js.php';
+include 'form-js.php';
 ?>
 <script>
     $('#backup-secondary .typecho-option-tabs li').click(function() {