feat: create new mode to enable state sync with github repositories

[hcavarsan]

Added

• Synchronization of all port forwarding configurations with a GitHub repository.
  • Users can now share their configurations easily with other users by setting up Git synchronization.
  • The new "Configure Git Sync" menu option allows users to fill in their GitHub repository information.
  • New "Sync Settings" button to apply synchronization settings immediately.
  • "Synchronize Configurations" option added to the main screen for updating to the latest configurations from the configured repository.

Security

• Encrypted storage of confidential information like the API key using the local operating system's keyring mechanisms:

  • Keychain for macOS users.
  • Credential Manager for Windows users.
  • Secret Service for Linux users.

  closes https://github.com/hcavarsan/kftray/issues/108