v0.6.5

• More reliable message history saving:
  • Add listeners for SIGHUP, SIGTERM to exit cleanly on e.g. system shutdown
  • Backup history on every startup and read it next time if history gets corrupted
• Add a new URL format for linking with an existing signal account: sgnl://linkdevice instead of tsdevice:/
• Display errors from external commands, including those specified with custom arguments, e.g. --open-command
• Improve misclellaneous exceptions handling