Update changelog for kotlinx-metadata-jvm 0.6.0, add migration guide, and actualize ReadMe.md
Document releasing process
Co-authored-by: Alexander Udalov <Alexander.Udalov@jetbrains.com>
Merge-request: KT-MR-8206
Merged-by: Leonid Startsev <leonid.startsev@jetbrains.com>