Increase version to 2.9.0

CHANGELOG.md

@@ -10,6 +10,14 @@ number is used only for corrections to the OpenAPI specification, for example:
 typos, schema fixes, or adding examples.
 
 
+## [2.9.0]
+### Added
+* Transitive glossaries are now supported, bringing the number of supported
+  glossary pairs from 8 to 28.
+### Changed 
+* Supported XLIFF version 2.1 is now explicitly stated.
+
+
 ## [2.8.0]
 ### Added
 * Add Korean and Norwegian (Bokmål) languages.
@@ -76,6 +84,7 @@ typos, schema fixes, or adding examples.
 Initial release of the OpenAPI specification.
 
 
+[2.9.0]: https://github.com/DeepLcom/openapi/compare/v2.8.0...v2.9.0
 [2.8.0]: https://github.com/DeepLcom/openapi/compare/v2.7.0...v2.8.0
 [2.7.0]: https://github.com/DeepLcom/openapi/compare/v2.6.0...v2.7.0
 [2.6.0]: https://github.com/DeepLcom/openapi/compare/v2.5.0...v2.6.0