Set "type=button" for editor's toolbar buttons (#26510) (#26518)

Backport #26510 by @wxiaoguang

The editor usually is in a form, so the buttons should have
"type=button", avoid conflicting with the form's submit.

Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

web_src/js/features/comp/ComboMarkdownEditor.js

@@ -78,6 +78,8 @@ class ComboMarkdownEditor {
     for (const el of this.textareaMarkdownToolbar.querySelectorAll('.markdown-toolbar-button')) {
       // upstream bug: The role code is never executed in base MarkdownButtonElement https://github.com/github/markdown-toolbar-element/issues/70
       el.setAttribute('role', 'button');
+      // the editor usually is in a form, so the buttons should have "type=button", avoiding conflicting with the form's submit.
+      if (el.nodeName === 'BUTTON' && !el.getAttribute('type')) el.setAttribute('type', 'button');
     }
 
     const monospaceButton = this.container.querySelector('.markdown-switch-monospace');