RTL support in the opendocument/odt writer.
`dir: rtl` in metadata should set `style:writing-mode` on paragraph styles:
```
% pandoc -f markdown -t opendocument --template command/11301-styles.opendocument
---
dir: rtl
---
# Heading
Hello world.
> quoted
^D
Heading
Hello world.
quoted
```
An RTL `lang` in metadata implies RTL direction:
```
% pandoc -f markdown -t opendocument --template command/11301-styles.opendocument
---
lang: he
---
Hello world.
^D
Hello world.
```
`dir: ltr` in metadata overrides an RTL language:
```
% pandoc -f markdown -t opendocument --template command/11301-styles.opendocument
---
lang: he
dir: ltr
---
Hello world.
^D
Hello world.
```
A `dir` attribute on a div changes direction for its contents:
```
% pandoc -f markdown -t opendocument --template command/11301-styles.opendocument
Plain paragraph.
::: {dir=rtl}
RTL paragraph.
:::
After div.
^D
Plain paragraph.
RTL paragraph.
After div.
```