Thunderbird 91 support

Thunderbird  91 is now available. The following is status of compatibility checking of my add-ons. I do not have enough time to test add-ons so far. I only checked basic functionalities. Please let me know if you find problems on your environment.

Download the latest versions from here:

https://hogi.sakura.ne.jp/en/index.rhtml

• Maximize Message Pane
  v2.1.0 is released. Please update. Older versions do not work on TB91.
  
  
• Message Header Toolbar Customize
  v2.2.2 is released. Please update. Older versions also work on TB91 but they have small glitches.
  Print button does not work in older versions.
  
  
• Tag Popup
  Current v2.1.5 works with TB91. No need to update.
  
  
• Check and Send
  Current v2.0.18 works with TB91. No need to update.
  
  
• Priority Switcher
  v2.0.5 is released. Please update. Delete functionality does not work in older versions.
  
  
• New Tab Button
  Current v2.0.6 works with TB91. No need to update.
  
  
• EnForward
  Does not work with TB91 so far. Please disable it on TB91.
  v2.1.0 is released. Please update.
  
  
  
• Evernote Tab
  Current v2.0.2 works with TB91. No need to update.