[Feature Request] [listbox] ctrl and shift key combinations multiselect

[tlouisse]

When we implement this, along with the type-ahead, I think we got all wai-aria listbox specs implemented (probably for the select-rich as well) 👍

Specs

Multiple Selection: Authors may implement either of two interaction models to support multiple selection: a recommended model that does not require the user to hold a modifier key, such as Shift or Control, while navigating the list or an alternative model that does require modifier keys to be held while navigating in order to avoid losing selection states.
Recommended selection model -- holding modifier keys is not necessary:
Space: changes the selection state of the focused option.
Shift + Down Arrow (Optional): Moves focus to and toggles the selected state of the next option.
Shift + Up Arrow (Optional): Moves focus to and toggles the selected state of the previous option.
Shift + Space (Optional): Selects contiguous items from the most recently selected item to the focused item.
Control + Shift + Home (Optional): Selects the focused option and all options up to the first option. Optionally, moves focus to the first option.
Control + Shift + End (Optional): Selects the focused option and all options down to the last option. Optionally, moves focus to the last option.
Control + A (Optional): Selects all options in the list. Optionally, if all options are selected, it may also unselect all options.
Alternative selection model -- moving focus without holding a Shift or Control modifier unselects all selected nodes except the focused node:
Shift + Down Arrow: Moves focus to and toggles the selection state of the next option.
Shift + Up Arrow: Moves focus to and toggles the selection state of the previous option.
Control + Down Arrow: Moves focus to the next option without changing its selection state.
Control + Up Arrow: Moves focus to the previous option without changing its selection state.
Control + Space Changes the selection state of the focused option.
Shift + Space (Optional): Selects contiguous items from the most recently selected item to the focused item.
Control + Shift + Home (Optional): Selects the focused option and all options up to the first option. Optionally, moves focus to the first option.
Control + Shift + End (Optional): Selects the focused option and all options down to the last option. Optionally, moves focus to the last option.
Control + A (Optional): Selects all options in the list. Optionally, if all options are selected, it may also unselect all options.

See: https://www.w3.org/TR/wai-aria-practices/#Listbox