Add missing version links

Author: cschwan

CHANGELOG.md

@@ -708,6 +708,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - first release
 
 [Unreleased]: https://github.com/NNPDF/pineappl/compare/v0.8.2...HEAD
+[0.8.6]: https://github.com/NNPDF/pineappl/compare/v0.8.5...v0.8.6
+[0.8.5]: https://github.com/NNPDF/pineappl/compare/v0.8.4...v0.8.5
 [0.8.4]: https://github.com/NNPDF/pineappl/compare/v0.8.3...v0.8.4
 [0.8.3]: https://github.com/NNPDF/pineappl/compare/v0.8.2...v0.8.3
 [0.8.2]: https://github.com/NNPDF/pineappl/compare/v0.8.1...v0.8.2