v3.23.0

🎉 It's our 1000th commit!!! 🌟 

## Features

- Support for Wireguard (#565)
  - For Mullvad (#565)
  - For Windscribe (#565)
- Wireguard works with kernel space or user space if unavailable
- `VPN_TYPE` variable
- `WIREGUARD_PRIVATE_KEY` variable
- `WIREGUARD_ADDRESS` variable
- `WIREGUARD_PRESHARED_KEY` variable
- `WIREGUARD_PORT` variable
- `OPENVPN_INTERFACE` defaulting to `tun0`

## Bug fixes

- Change ownership of OpenVPN configuration file with `PUID` and `PGID`
- OpenVPN custom config process user gets removed
- OpenVPN custom config with custom network interface name set properly in firewall
- Sorted IP addresses for servers.json (#574)
- Only allow traffic through VPN interface when needed

## Documentation

- Update readme
  - Image size lowered to 31MB
  - Using Alpine 3.14
  - Wireguard support

## Changes

- HTTP control server `/v1/openvpn` route interacts with OpenVPN settings only (not provider settings)

## Maintenance

- `internal/vpn` package for vpn loop (OpenVPN and Wireguard)
- `internal/netlink` package used by `internal/wireguard`
- Improve `internal/configuration` code
- Read all settings first
- Context aware `collectLines` functions
- `internal/tun` package to handle tun device operations
  - TUN check verifies `Rdev` value of file
  - Inject as interface to main function
  - Add integration test
  - Clearer log message for end users if tun device does not exist
  - Remove tun file opening at the end of tun file creation
- Remove unix package (unneeded for tests)
- Do not mock unix.Mkdev (no OS operation)
- `internal/openvpn/custom` package for custom configuration with tests
- Better log when catching an OS signal
- Fix logger settings inheritance
- Keep VPN tunnel interface name in firewall state
- Upgrade from Go 1.16 to Go 1.17