v0.7.0

• Sort messages by local timestamps (#113).
• Implement:
  • Sending reactions.
  • Sending remote-delete (remove for everybody in chat) messages.
  • Receiving stickers.
• Improve notifications:
  • Show sender's avatar in desktop notifications.
  • Send a terminal-bell signal to highlight the terminal's window.
• Packaging: automatically include a static code archive in the release assets (to address #143, #151).