Make repository a nix flake

Make git-email.el a nix flake for an easier installation process for
Nix users.  It currently exposes two packages:

- git-email-full -- This includes all the optional libraries
- git-email -- This only includes the core `git-email.el` library

They both get the source from directory from the git repository,
meaning they will get updates as soon as a commit is made.

* default.nix: Add file.
* flake.lock: Add file.
* flake.nix: Add file.

1 files changed, 43 insertions, 0 deletions

diff --git a/flake.lock b/flake.lock
new file mode 100644
index 0000000..52c007e
--- /dev/null
+++ b/flake.lock
@@ -0,0 +1,43 @@
+{
+  "nodes": {
+    "flake-utils": {
+      "locked": {
+        "lastModified": 1610051610,
+        "narHash": "sha256-U9rPz/usA1/Aohhk7Cmc2gBrEEKRzcW4nwPWMPwja4Y=",
+        "owner": "numtide",
+        "repo": "flake-utils",
+        "rev": "3982c9903e93927c2164caa727cd3f6a0e6d14cc",
+        "type": "github"
+      },
+      "original": {
+        "owner": "numtide",
+        "repo": "flake-utils",
+        "type": "github"
+      }
+    },
+    "nixpkgs": {
+      "locked": {
+        "lastModified": 1612407036,
+        "narHash": "sha256-3wFGXSK9tQU/6dPfwjNUxygeZCbYxe0O0JXVyj1G2tk=",
+        "owner": "nixos",
+        "repo": "nixpkgs",
+        "rev": "04d5f1e3a87d413181af5d6dd68568228addf1c3",
+        "type": "github"
+      },
+      "original": {
+        "owner": "nixos",
+        "ref": "nixpkgs-unstable",
+        "repo": "nixpkgs",
+        "type": "github"
+      }
+    },
+    "root": {
+      "inputs": {
+        "flake-utils": "flake-utils",
+        "nixpkgs": "nixpkgs"
+      }
+    }
+  },
+  "root": "root",
+  "version": 7
+}