Changes in Thunderbird 90
cloudFile
added support for the
browser_style
manifest property to the cloudFile API
compose
added sendMessage(tabId, [options]) function
added getComposeState(tabId) function
added onComposeStateChanged event
added ComposeState type
added
redirect
enum to type property of ComposeDetails
messages
added
size
property to the MessageHeader
Bugzilla list of fixed WebExtension API defects in Thunderbird 90.