This implement the flexbox elements, following the HTML one.
Built from them, there is also the following elements:
- `paragraph`
- `paragraphAlignLeft`
- `paragraphAlignRight`
- `paragraphAlignCenter`
- `paragraphAlignJustify`
This is a breaking change.
Dom
- `vscroll_indicator`. Show a scrollback indicator on the right.
Component
- `Maybe`: Display an component conditionnally based on a boolean.
- `Dropdown`: A dropdown select list.
This address:
https://github.com/ArthurSonzogni/FTXUI/issues/204
