[FR] Add Mail to Task

### Description

The feature should allow to connect a mail account (manually via credentials as well as already established identity providers like google) to appflowy and an inbox view should be accessible via a button in the Sidebar or top right corner.
The inbox view should loosely reflect what apple mail offers ui-wise. Mails should be markable as read/unread, sortable, filterable by text, and rules for sorting the mails automatically in specific folders should be applicable.

The mail login should also offer the possibility to import any amount of calendars into appflowy. For the cloud, the access to the calendar would need to be given to others before they can see it.

From the mail view, users should be able to right click / long tap an email for a context menu that should offer creating a new task from this mail. The mail would be added as an attachment to the task so everybody seeing the task can also see the email.
Also, an option should be present to create a new document or space from the mail contents (this needs more fleshing out)

### Impact

I like appflowy pretty much. What I am still missing is the possibility to create tasks directly from my mails (or link mails to tasks)
So I can use appflowy as one-for-all tool for my planning, documentation and coordination.
Afaik, Notion has something to import mails, but it is pretty lackluster.

### Additional Context

I only was able to roughly flesh out the feature. I would be happy to plan and elaborate more with others on specifics as well as mockups on how this feature could look.
I would appreciate if this feature could get added to the scope of appflowy.