Add empty CHANGELOG

The CHANGELOG generator we use:
https://github.com/github-changelog-generator/github-changelog-generator
has stopped working with errors like the following:

Warning: PR 3148 merge commit was not found in the release branch or tagged git history and no rebased SHA comment was found

So we'll defer populating the CHANGELOG summary until after the release

CHANGELOG.md

@@ -4,6 +4,10 @@
 <img align="right" width="300" height="300" alt="Juvix Mascot" src="../assets/images/tara-smiling.svg" />
 </a>
 
+## [v0.6.8](https://github.com/anoma/juvix/tree/v0.6.8) (2024-11-11)
+
+[Full Changelog](https://github.com/anoma/juvix/compare/v0.6.7...v0.6.8)
+
 ## [v0.6.7](https://github.com/anoma/juvix/tree/v0.6.7) (2024-11-06)
 
 [Full Changelog](https://github.com/anoma/juvix/compare/v0.6.6...v0.6.7)