Pin Prettier plug-in version in GitHub action (#351)
Pin Prettier plug-in version in GitHub action (#351)

[prettier/plugin-xml](https://github.com/prettier/plugin-xml) dropped support for the `xmlSelfClosingSpace` option in [v1.0.0](https://github.com/prettier/plugin-xml/blob/main/CHANGELOG.md#100---2021-07-14), which causes formatting checks to fail until the extra space is added to self-closing elements.

This commit pins the plug-in version to the last version that supports the `xmlSelfClosingSpace` option to allow checks to complete successfully and work around the regression in https://github.com/prettier/plugin-xml/issues/11.

Signed-off-by: Roger Sheen <a61a1add71dadc74037ae5e44ee30713db9a7451@infotexture.net>
dita-ot/docs