add nix flake configuration

Introduce `flake.nix` and `flake.lock` to support building the Rust
project using the Nix flakes system. This includes specifying
dependencies, using the nightly Rust toolchain, and setting up necessary
build inputs such as OpenSSL.

.github/workflows/main.yaml

@@ -71,6 +71,31 @@ jobs:
             target/${{ matrix.target }}/release/neuronek-cli
             target/${{ matrix.target }}/release/neuronek-cli.exe
 
+  nix_build:
+    name: "Nix Build"
+    runs-on: "ubuntu-latest"
+    steps:
+      - uses: actions/checkout@v4
+
+      # Install Nix
+      - uses: cachix/install-nix-action@v24
+        with:
+          nix_path: nixpkgs=channel:nixos-unstable
+
+      # Build with Nix
+      - name: Build with Nix
+        run: nix build
+
+      # Optional: Run tests
+      - name: Run Nix tests
+        run: nix flake check
+
+      # Optional: Save build result as artifact
+      - name: Upload build result
+        uses: actions/upload-artifact@v3
+        with:
+          name: nix-build-result
+          path: ./result
 
 # Disabled until automatic versioning will be configured
 #  cargo_release:

.github/workflows/release.yml

@@ -335,3 +335,25 @@ jobs:
       - uses: actions/checkout@v4
         with:
           submodules: recursive
+
+  nix_package:
+    needs: [plan]
+    runs-on: "ubuntu-latest"
+    steps:
+      - uses: actions/checkout@v4
+
+      # Install Nix
+      - uses: cachix/install-nix-action@v24
+        with:
+          nix_path: nixpkgs=channel:nixos-unstable
+
+      # Build package
+      - name: Build Nix package
+        run: nix build .#packages.x86_64-linux.default
+
+      # Upload package
+      - name: Upload Nix package
+        uses: actions/upload-artifact@v3
+        with:
+          name: nix-package
+          path: ./result

.gitignore

@@ -88,7 +88,7 @@ target/
 
 # Remove Cargo.lock from gitignore if creating an executable, leave it for libraries
 # More information here https://doc.rust-lang.org/cargo/guide/cargo-toml-vs-cargo-lock.html
-Cargo.lock
+# Cargo.lock
 
 # These are backup files generated by rustfmt
 **/*.rs.bk

CONTRIBUTING.md

@@ -0,0 +1,12 @@
+# Contribution Guidelines
+
+```
+# Enter development shell
+nix develop
+
+# Build project
+nix build
+
+# Run continuous checks
+bacon
+```