feat(ci/cd): Set up Hydra

.hydra/jobsets.nix

@@ -0,0 +1,13 @@
+{ nixpkgs ? <nixpkgs> }:
+
+let
+
+  pkgs = import nixpkgs { };
+
+in
+
+{
+
+  myapp = pkgs.writeShellScript "hello" "${pkgs.hello}/bin/hello";
+
+}

.hydra/spec.json

@@ -0,0 +1,25 @@
+{
+  "hello": {
+    "enabled": 1,
+    "hidden": false,
+    "description": "ZSH flake",
+    "nixexprinput": "src",
+    "nixexprpath": ".hydra/jobsets.nix",
+    "checkinterval": 300,
+    "schedulingshares": 100,
+    "enableemail": false,
+    "emailoverride": "",
+    "keepnr": 3,
+    "inputs": {
+      "src": {
+        "type": "git",
+        "value": "git://forgejo.stefka.eu/jiriks74/zsh.nix.git main",
+        "emailresponsible": false 
+      },
+      "nixpkgs": { "type": "git",
+        "value": "git://github.com/NixOS/nixpkgs.git release-16.03",
+        "emailresponsible": false
+      }
+    }
+  }
+}