add componentList to works schema

[peterstadler]

as discussed with @solveigschreiter and @cmvweber at our face2face on 2024-02-19.

[peterstadler]

some example <componentList> that could be added as last child of <work>:

<componentList type="virtual">
   <work codedval="A351234">
      <title>Cavatine der Euryanthe</title>
      <title type="alt">Glöcklein</title>
      <classification>
         <termList>
            <term>Cavatine</term>
            <term>ggf. weitere Begriffe</term>
         </termList>
      </classification>
   </work>
</componentList>