flake.nix: update flake inputs

- Added stable branch for nixpkgs. This is for the preparation of
  facilitating creating hosts that is more maintainable with stable
  branches (like servers, for example).

- Update nixpkgs URL for Neovim overlay. The workaround is based from
  the following link at
  https://github.com/nix-community/neovim-nightly-overlay/issues/164#issuecomment-1377562202

flake.lock

@@ -410,9 +410,7 @@
       "inputs": {
         "flake-compat": "flake-compat_2",
         "neovim-flake": "neovim-flake",
-        "nixpkgs": [
+        "nixpkgs": "nixpkgs_2"
-          "nixpkgs"
-        ]
       },
       "locked": {
         "lastModified": 1673770422,
@@ -577,6 +575,22 @@
       }
     },
     "nixpkgs-stable": {
+      "locked": {
+        "lastModified": 1673704454,
+        "narHash": "sha256-5Wdj1MgdOgn3+dMFIBtg+IAYZApjF8JzwLWDPieg0C4=",
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "a83ed85c14fcf242653df6f4b0974b7e1c73c6c6",
+        "type": "github"
+      },
+      "original": {
+        "owner": "NixOS",
+        "ref": "nixos-22.11",
+        "repo": "nixpkgs",
+        "type": "github"
+      }
+    },
+    "nixpkgs-stable_2": {
       "locked": {
         "lastModified": 1673740915,
         "narHash": "sha256-MMH8zONfqahgHly3K8/A++X34800rajA/XgZ2DzNL/M=",
@@ -593,6 +607,22 @@
       }
     },
     "nixpkgs_2": {
+      "locked": {
+        "lastModified": 1671983799,
+        "narHash": "sha256-Z2Ro6hFPZHkBqkVXY5/aBUzxi5xizQGvuHQ9+T5B/ks=",
+        "owner": "nixos",
+        "repo": "nixpkgs",
+        "rev": "fad51abd42ca17a60fc1d4cb9382e2d79ae31836",
+        "type": "github"
+      },
+      "original": {
+        "owner": "nixos",
+        "repo": "nixpkgs",
+        "rev": "fad51abd42ca17a60fc1d4cb9382e2d79ae31836",
+        "type": "github"
+      }
+    },
+    "nixpkgs_3": {
       "locked": {
         "lastModified": 1673631141,
         "narHash": "sha256-AprpYQ5JvLS4wQG/ghm2UriZ9QZXvAwh1HlgA/6ZEVQ=",
@@ -638,7 +668,8 @@
         "nix-colors": "nix-colors",
         "nix-ld": "nix-ld",
         "nixos-generators": "nixos-generators",
-        "nixpkgs": "nixpkgs_2",
+        "nixpkgs": "nixpkgs_3",
+        "nixpkgs-stable": "nixpkgs-stable",
         "nur": "nur",
         "rust-overlay": "rust-overlay_2",
         "sops-nix": "sops-nix"
@@ -694,7 +725,7 @@
         "nixpkgs": [
           "nixpkgs"
         ],
-        "nixpkgs-stable": "nixpkgs-stable"
+        "nixpkgs-stable": "nixpkgs-stable_2"
       },
       "locked": {
         "lastModified": 1673752321,

flake.nix

@@ -13,6 +13,7 @@
     # `nixpkgs-unstable` branch could be faster delivering updates, it is
     # looser when it comes to stability for the entirety of this configuration.
     nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
+    nixpkgs-stable.url = "github:NixOS/nixpkgs/nixos-22.11";
 
     # We're using these libraries for other functions.
     flake-utils.url = "github:numtide/flake-utils";
@@ -52,7 +53,7 @@
     # We're getting more unstable there should be a black hole at my home right
     # now. Also, we're seem to be collecting text editors like it is Pokemon.
     neovim-nightly-overlay.url = "github:nix-community/neovim-nightly-overlay";
-    neovim-nightly-overlay.inputs.nixpkgs.follows = "nixpkgs";
+    neovim-nightly-overlay.inputs.nixpkgs.url = "github:nixos/nixpkgs?rev=fad51abd42ca17a60fc1d4cb9382e2d79ae31836";
 
     emacs-overlay.url = "github:nix-community/emacs-overlay";
     emacs-overlay.inputs.nixpkgs.follows = "nixpkgs";