Add a task adding widget

I would really like a widget to add tasks with. Essentially just the add task bar currently in the app, as a widget. This would allow you to add tasks directly from any screen supporting widgets. And combined with something like WidgetDrawer (now part of Lockscreen widgets) you could add tasks from anywhere!

Start by locating the existing add-task bar in the app and reviewing how the project handles mobile widgets. Compare the widget's scope with the mentioned WidgetDrawer and lockscreen-widget use cases; done means providing a usable widget that can add tasks from supported screens.

Written by the indexing model from the issue text.