doc: Avoid Windows reserved filesystem name by renaming aux to auxiliary

Closes #77

doc/changes/.proclamation.json

@@ -22,7 +22,7 @@
             "directory": "compositor"
         },
         "Helper Libraries": {
-            "directory": "aux"
+            "directory": "auxiliary"
         },
         "Misc. Features": {
             "directory": "misc_features"

doc/changes/misc_fixes/mr.314.md

@@ -0,0 +1,4 @@
+Way way back when Gallium was made `auxiliary` was named `aux` but then it was
+ported to Windows and it was renamed to `auxiliary`. Through the ages this
+knowlage was lost and so we find ourselves with with the same problem, tho
+Monado inheritated the correct name the same mistake was made in docs.