ci: Init some CIs

.github/workflows/fetch-releases.yml

@@ -0,0 +1,17 @@
+name: fetching-releases
+on:
+  schedule:
+    - cron: '0 */12 * * *'
+  workflow_dispatch:
+jobs:
+  update-sources:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/[email protected]
+      - uses: cachix/install-nix-action@v26
+        with:
+          nix_path: nixpkgs=channel:nixos-unstable
+      - run: ./fetch-releases.py
+      - uses: stefanzweifel/[email protected]
+        with:
+          commit_message: "ci: Update sources.json"

.github/workflows/nix-flake-check.yml

@@ -0,0 +1,13 @@
+on: [push, pull_request]
+name: nix-flake-check
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/[email protected]
+      - uses: cachix/install-nix-action@v26
+        with:
+          nix_path: nixpkgs=channel:nixos-unstable
+      - run: nix flake check
+
+      - run: ./fetch-releases.py