flake.lock: Update

Flake input changes:

* Updated 'nix': 'github:NixOS/nix/eb75282b8dc855983368c79cc4c2943c298518f7' -> 'github:NixOS/nix/2a8017092025a7c108ca1a829a8b4f0bcf7ee2c0'
* Added 'nix/lowdown-src': 'github:edolstra/lowdown/c7a4e715af1e233080842db82d15b261cb74cb28'

flake.lock

@@ -1,15 +1,33 @@
 {
   "nodes": {
+    "lowdown-src": {
+      "flake": false,
+      "locked": {
+        "lastModified": 1598296217,
+        "narHash": "sha256-ha7lyNY1d8m+osmDpPc9f/bfZ3ZC1IVIXwfyklSWg8I=",
+        "owner": "edolstra",
+        "repo": "lowdown",
+        "rev": "c7a4e715af1e233080842db82d15b261cb74cb28",
+        "type": "github"
+      },
+      "original": {
+        "owner": "edolstra",
+        "ref": "no-structs-in-anonymous-unions",
+        "repo": "lowdown",
+        "type": "github"
+      }
+    },
     "nix": {
       "inputs": {
+        "lowdown-src": "lowdown-src",
         "nixpkgs": "nixpkgs"
       },
       "locked": {
-        "lastModified": 1598539168,
+        "lastModified": 1600161919,
-        "narHash": "sha256-2i95APppDPjN7wKfgJHlg9r7vU13vOI22iK88mtuvy4=",
+        "narHash": "sha256-kfxiAdd/CK09M5i2WeBbTIxDenAdlqDLkhsrMZy8qQo=",
         "owner": "NixOS",
         "repo": "nix",
-        "rev": "eb75282b8dc855983368c79cc4c2943c298518f7",
+        "rev": "2a8017092025a7c108ca1a829a8b4f0bcf7ee2c0",
         "type": "github"
       },
       "original": {