Preserve positioning with {\an8}

some xml based subtitles has region field, that specifies if the text is supposed to appear on the top or the bottom.
{\an8}, though not a native tag for srt, works with most players to display text on the top.
```
<layout>
<region tts:displayAlign="before" xml:id="region0"/>
<region tts:displayAlign="after" xml:id="region1"/>
</layout>
```