Linking between tasks

[jg10-mastodon-social]

I don't think this is possible yet within Focus, though it is possible to link to the underlying data outside of focus.

In the description for one task, I'd like to be able to link to another task and have it open in Focus.

As a bonus, it would be great if the implementation allowed other apps to link to the task in Focus, as discussed in #22 (comment) and in the spirit of #16

I'm partly opening this new issue because #22 was solved without requiring implementation of deep linking to tasks 😉