Add Elvish unstressed words to list files

I went through the conjunctions and prepositions listed in the Ambar
Eldaron Quenya Dictionary [1] and the Omikhleia Sindarin Dictionary [2]
and added all the ones with a single light syllable to the list as
unstressed (with one exception). I think this improves the way some
texts are read a little bit (though I have to admit I find it hard to
tell the difference).

[1]: https://ambar-eldaron.com/telechargements/quenya-engl-A4.pdf
[2]: https://www.jrrvf.com/hisweloke/sindar/index.html

dictsource/qya_list

+// words with a single light syllable which should not be stressed
+
+// conjunctions:
+a	$u
+an	$u
+ar	$u
+hya	$u
+i	$u
+mal	$u
+nan	$u
+o	$u
+qui	$u
+ta	$u
+var	$u
+// prepositions:
+et	$u
+han	$u
+ho	$u
+lo	$u
+mi	$u
+mil	$u
+no	$u
+nu	$u
+or	$u
+pa	$u
+po	$u
+tar	$u
+ter	$u
+va	$u
+ve	$u
+yo	$u

dictsource/sjn_list

 imladris	$1 // Seek for the Sword that was broken, line 2
 menegroþ	$1 // Lay of Leithian Recommenced, line 65
 nargoþrond	$1 // The world was young, the mountains green, line 13
+
+// words with a single light syllable which should not be stressed
+
+// conjunctions:
+// a – exception: also an interjection, should still be stressed then
+ach	$u
+ah	$u
+ir	$u
+sui	$u
+// prepositions:
+am	$u
+an	$u
+ben	$u
+bo	$u
+dan	$u
+na	$u
+ned	$u
+nef	$u
+nu	$u
+o	$u
+or	$u
+os	$u
+pen	$u
+vi	$u