A button that opens a menu of filter groups; a group opens a submenu of ticks, checkboxes or radios. Ticking
does not close the menu. The menu is a form: it sends on Apply (phx-submit), or on every tick with
phx-change, as %{"filters" => %{"status" => ["progress"], "who" => ["CA"]}}. A count on each group and on the
button follows the ticks, except for an option marked default, which is what the filter already means.
A group is %{key: "status", label: "Status", type: :checkbox, options: [...]} and an option is
%{value: "progress", label: "In progress", count: 2, checked: true, default: false, avatar: "CA"}; count,
checked, default and avatar are optional. Arrows move, → opens a submenu, ← and Esc go back, Enter and
Space tick. Words are attributes and icons are slots.