Release v3.19.0 (#62)

* Prepare release v3.19.0

* Update the state.json for v3.19.0

* Update README.md and action.yml for v3.19.0

* flake.lock: Update

Flake lock file updates:

• Updated input 'nixpkgs':
    'https://api.flakehub.com/f/pinned/NixOS/nixpkgs/0.1.982522%2Brev-b12141ef619e0a9c1c84dc8c684040326f27cdcc/019dac49-3fcc-79b0-85fb-7ee694b1cf62/source.tar.gz' (2026-04-18)
  → 'https://api.flakehub.com/f/pinned/NixOS/nixpkgs/0.1.987561%2Brev-1c3fe55ad329cbcb28471bb30f05c9827f724c76/019dd544-2f5a-70b0-a89a-cf26aa85b1a7/source.tar.gz' (2026-04-27)

---------

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>

action.yml

@@ -72,7 +72,7 @@
         "source-tag": {
             "description": "The tag of `nix-installer` to use (conflicts with `source-revision`, `source-branch`, `source-pr`)",
             "required": false,
-            "default": "v3.18.1"
+            "default": "v3.19.0"
         },
         "source-url": {
             "description": "A URL pointing to a `nix-installer` executable",
@@ -105,7 +105,7 @@
         "using": "composite",
         "steps": [
             {
-                "uses": "DeterminateSystems/nix-installer-action@92148bb48b9a0c5458c53dd0b368fbfbfbaa3210",
+                "uses": "DeterminateSystems/nix-installer-action@4a754ab0c192f4d12cf88b5954b9dd13fd2d612e",
                 "with": {
                     "extra-conf": "${{ inputs.extra-conf }}",
                     "github-server-url": "${{ inputs.github-server-url }}",