Add e-mail provider "Strato.de"

Hi,
in Germany "Strato.de" is one of the biggest e-mail (and homepage) provider. Could you add this please? I think it belongs into /[src](https://github.com/joplin/plugin-email/tree/main/src)/[core](https://github.com/joplin/plugin-email/tree/main/src/core)/emailProviders.ts

```
{
type: 'Strato',
host: 'imap.strato.de',
port: 993,
tls: true,
},
```

Thank's a lot,
Christian