fix(scripts): vendor files causing reloads

Ignore the `vendor` directory and some others as it was causing the
script to reload when it wasn't expected.

Whilst I'd expect it to be ignored if I specified the path to look at as
something like `web/modules/custom`, but it still seems to trigger the
command and it seems a lot more stable since adding this.

bin/watch-changes

@@ -11,6 +11,7 @@ while true; do
   inotifywait \
     --event modify \
     --event move_self \
+    --exclude ".git|simpletest|vendor" \
     --recursive \
     $1 && $2
 done