Import all projects and tasks/issues from Gitlab/Github user

[rommeswi]

I think it would be a major convenience feature if it was possible to just provide Gitlab/Github access and superproductivity retrieves all projects and all issues in these projects as tasks.

This idea was previously reported as a bug in #3523

I am wondering if there are any good reasons that speak against this. Perhaps API limitations or task overload?

[johannesjo]

Would be cool to have a button for this on the github settings page! PRs are welcome!