feat(alcoholic_jwt): Add Nix build for crate

... mostly to get CI.

Note that this adds the Cargo.lock file because we require pinning,
but it is generally not required for Rust libraries.

Change-Id: Iedbd3758e8df8a7f60fe67b6b06c8e41aba8f345
Reviewed-on: https://cl.tvl.fyi/c/depot/+/3362
Reviewed-by: tazjin <mail@tazj.in>
Tested-by: BuildkiteCI

net/alcoholic_jwt/default.nix

@@ -0,0 +1,9 @@
+{ depot, pkgs, ... }:
+
+depot.third_party.naersk.buildPackage {
+  src = ./.;
+  buildInputs = with pkgs; [
+    openssl
+    pkgconfig
+  ];
+}