[Thunderbird] Add the option to synchronise email when opening the application.

[Almorca]

Some users do not want to receive emails on the phone at regular intervals; instead, we want to decide for ourselves when to check for new messages.
Currently, to do this, you have to set the synchronisation to never, open the application, and synchronise manually.
To simplify this process, it would be useful to have an option for #Thunderbird Android to automatically synchronise accounts when you open it

[Jon]

Thanks for submitting an idea to the Mozilla Connect community! Your idea is now open to votes (aka kudos) and comments.