Add NordVPN as provider

[jeff-hughes]

Adding NordVPN to the list of providers. Note that this is only supported via OpenVPN. For wireguard, they've built an extra layer on top of it called NordLynx, which is intended to avoid having to store identifiable data on their servers. Unfortunately, they don't currently have any documentation on how to set up wireguard to connect to NordLynx. It's set up in their Linux client, but I don't know enough about wireguard config to be able to dig further to try to find out more details.

[jamesmcm]

Thanks, it looks great.

Could you please fix the clippy errors? And I'll merge it.

https://rust-lang.github.io/rust-clippy/master/index.html#match_like_matches_macro

   --> src/providers/nordvpn/openvpn.rs:155:9
    |
155 | /         match self {
156 | |             Self::OnionTcp => true,
157 | |             Self::OnionUdp => true,
158 | |             _ => false,
159 | |         }
    | |_________^ help: try this: `matches!(self, Self::OnionTcp | Self::OnionUdp)`
    |
    = note: `-D clippy::match-like-matches-macro` implied by `-D warnings`
    = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#match_like_matches_macro

error: match expression looks like `matches!` macro
   --> src/providers/nordvpn/openvpn.rs:163:9
    |
163 | /         match self {
164 | |             Self::DoubleTcp => true,
165 | |             Self::DoubleUdp => true,
166 | |             _ => false,
167 | |         }
    | |_________^ help: try this: `matches!(self, Self::DoubleTcp | Self::DoubleUdp)`
    |
    = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#match_like_matches_macro```

[jeff-hughes]

There we go -- this was a reminder that I hadn't updated Rust (and clippy) in a while :)

[jamesmcm]

Thanks! I bumped the version so it can build a new release too.