update nix flakes, gh workflows and docs

.github/workflows/pre-release.yml

@@ -0,0 +1,51 @@
+name: pre-release
+
+on:
+  push:
+
+jobs:
+  pre-release:
+    runs-on: ${{ matrix.os }}
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          - target: x86_64-linux
+            os: ubuntu-latest
+          - target: aarch64-linux
+            os: ubuntu-latest
+          - target: x86_64-windows
+            os: ubuntu-latest
+          - target: x86_64-darwin
+            os: macos-13
+          - target: aarch64-darwin
+            os: macos-14
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v4
+      - name: Install Nix
+        uses: cachix/install-nix-action@v27
+        with:
+          nix_path: nixpkgs=channel:nixos-24.05
+          enable_kvm: true
+          extra_nix_config: "experimental-features = nix-command flakes"
+      - name: Cache Nix store
+        uses: cachix/cachix-action@v15
+        with:
+          name: soywod
+          authToken: '${{ secrets.CACHIX_AUTH_TOKEN }}'
+          extraPullNames: nix-community
+      - name: Build release
+        run: |
+          nix build -L .#${{ matrix.target }}
+          nix run -L .#${{ matrix.target }} -- --version
+      - name: Upload release artifact (tarball)
+        uses: actions/upload-artifact@v4
+        with:
+          name: "himalaya.${{ matrix.target }}.tgz"
+          path: result/himalaya.tgz
+      - name: Upload release artifact (zip)
+        uses: actions/upload-artifact@v4
+        with:
+          name: "himalaya.${{ matrix.target }}.zip"
+          path: result/himalaya.zip