Add release for aarch64

This release changes the naming scheme of the downloads. This makes it possible to download upduck on a Raspberry Pi like with the following command:

arch=$(uname -m) && wget -O upduck "https://github.com/xarantolus/upduck/releases/latest/download/upduck-raspberrypi-${arch%l}"

There's now also a release build for aarch64, the architecture of the Raspberry Pi 4.

Update dependencies

• Updates all dependencies
• Switch to libdns

To upgrade, just download (or clone & build) the appropriate executable for your system and replace the current one. There's no need to change the configuration.

User accounts

Changes:

• Serve index.html file if found in a directory
• Display the local server address when starting.(Sadly we cannot know the public address as we don't know which port was forwarded).
• Build different versions for different Raspberry Pis

New:

• Add optional user logins:

  Create a new user account (or replace an existing one):

  upduck adduser <username> <password>
  

  Delete a user:

  upduck deluser <username>
  

  Reset all user logins:

  upduck resetusers
  

  If any user accounts are configured, you need to log in before accessing files.

Enhancements

This release includes several new features:

• Dark mode: the directory listing site is now in a dark+green theme
• Directory downloads: directories can be downloaded as zip, tar or tar.gz files. If -disallow-listings is given, downloads will be disabled

Initial Release

This release contains all basic features:

• HTTP file server (for local network)
• HTTPS file server combined with DuckDNS domain (for outside access)
• Saving & Restoring settings is possible