Keyboard-driven method for reordering rows

This idea was brought up before:

          It would also be massively useful when trying to provide a keyboard-driven alternative method for reordering rows, for use by the vision-impaired or others with special needs.

Originally posted by @QuixoteOne in https://github.com/DataTables/RowReorder/issues/10#issuecomment-275780532

We want to provide row reordering functionality for our users, but if it doesn't work via the keyboard, we wouldn't be able to provide an equitable experience for our users. It would also open us up to legal concerns.

As far as implementation:

• The draggable selector needs to be focusable
• A keyboard shortcut that is already popular for manual sorting (for example, Google Tasks seems to use Ctrl-UpArrow and Ctrl-DownArrow)
• Optional: For the keyboard, the position calculations shouldn't need to use X/Y coordinates. Thus, it may be good to segment the existing code such that the "where did the mouse/drag start/end" code that calculates the old and new positions is separate from the "change row position" code.

Thank you for considering this request! ❤️

Start by locating the draggable selector and the existing row-position calculations, then determine how the mouse or drag start/end logic is separated from changing row order. Done means the reorder control is keyboard-focusable and supports an agreed keyboard shortcut without relying on X/Y coordinates, with equivalent row reordering behavior.