Prepare 0.6.1 release

[evdokimovs]

Synopsis

Prepares 0.6.1 release.

Checklist

• Created PR:
  • [x] In draft mode
  • [x] Name contains issue reference
  • [x] Has type and k:: labels applied
  • [x] Has assignee
• Before review:
  • [x] Documentation is updated (if required)
  • [x] Tests are updated (if required)
  • [x] Changes conform code style
  • [x] CHANGELOG entry is added (if required)
  • [x] FCM (final commit message) is posted or updated
  • [x] Draft mode is removed
• [x] Review is completed and changes are approved
  • [x] FCM (final commit message) is approved
• Before merge:
  • [x] Milestone is set
  • [x] PR's name and description are correct and up-to-date
  • [x] All temporary labels are removed

[evdokimovs]

FCM

Prepare 0.6.1 release of `medea-jason` crate and `medea_jason` Dart package (#186)