Merge branch '29-use-activity-buttons-widgets-from-flutter_custom_toolbox' into 'master'

Resolve "Use activity buttons widgets from flutter_custom_toolbox"

Closes #29

See merge request !29

resources/ui/images/button_start.svg

-<?xml version="1.0" encoding="UTF-8"?>
-<svg enable-background="new 0 0 100 100" version="1.1" viewBox="0 0 93.665 93.676" xml:space="preserve" xmlns="http://www.w3.org/2000/svg"><path transform="matrix(-1.3783 -.61747 .61747 -1.3783 46.954 -.086035)" d="m11.645-14.603-44.77-4.6003 26.369-36.472z" fill="#fff" stroke="#105ea2" stroke-linecap="round" stroke-linejoin="round" stroke-width="7.2832"/></svg>