Add support for additional event attendance types for the event from Google Calendar.

[krishhneer]

While marking attendance for the events on Thunderbird, there is only one option of 'Accept'. While Google Calendar supports two more additional options for the positive responses; 'Yes, in a meeting room' and 'Yes, joining virtually'.

It would be helpful if we mark attendance using any of these additional options within Thunderbird itself, so we can provide appropriate attendance details without opening Google Calendar.

[Jon]

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