PHP 7.4 required

This small upgrade release is mainly for a better Style integration with Nextcloud.
As benefit it would also be easier to make your own SnappyMail theme.

Bugfixes

• CSS --dropdown-menu-background-color should be --dropdown-menu-bg-color

Improvements

• Strip mailchimp tracking
• Use some PHP typed properties (PHP 7.4)
• Move bootstrap @less variables to CSS var()
• Improved theme styling

Integrations

https://github.com/the-djmaze/snappymail/wiki/Installation-instructions#integrations

Nextcloud

• Disable Nextcloud Impersonate check due to login/logout complications #561
• Improved theme integration and be compatible with Breeze Dark

https://apps.nextcloud.com/apps/snappymail

DockerHub

Read issue #44

Full Changelog: v2.19.7...v2.20.0