re­alscripts – Ac­cess OpenType sub­script and su­per­script glyphs

This small pack­age re­places \textsu­per­script and \textsub­script com­mands by equiv­a­lent com­mands that use OpenType font fea­tures to ac­cess ap­pro­pri­ate glyphs if pos­si­ble.
The pack­age also patches LaTeX’s de­fault foot­note com­mand to use this new \textsu­per­script for foot­note sym­bols.
The pack­age re­quires fontspec run­ning on ei­ther X∃LaTeX or LuaLaTeX.
The pack­age holds func­tions that were once parts of the xltx­tra pack­age, which now loads re­alscripts by de­fault.