Add default set of elements

[qeffects]

Create a limited set of default elements, for now:

1. Button with text
2. Button with icon and text
3. Textinput
4. Scrollbar
5. Scrollcontainer
6. Dropdown/combo box
7. Checkbox
8. Radio box

[qeffects]

I'll come up with a mock-up in figma and post it later.