Add support for nix-shell

.vscode/settings.json

@@ -0,0 +1,3 @@
+{
+  "nixEnvSelector.nixFile": "${workspaceFolder}/shell.nix"
+}

rust-toolchain.toml

@@ -0,0 +1,2 @@
+[toolchain]
+channel = "stable"

shell.nix

@@ -0,0 +1,30 @@
+{
+  pkgs ? import <nixpkgs> { },
+}:
+
+pkgs.mkShell {
+  buildInputs = [
+    pkgs.rustup
+  ];
+
+  shellHook = ''
+    DATA_DIR=/tmp/rust/lum
+    export RUSTUP_HOME=$DATA_DIR/rustup
+    export CARGO_HOME=$DATA_DIR/cargo
+    export PATH=$CARGO_HOME/bin:$PATH
+    mkdir -p $CARGO_HOME
+    mkdir -p $RUSTUP_HOME
+
+    rustup default stable
+    rustup update
+    cargo fetch
+
+    echo
+    echo
+    echo
+
+    echo "Rustup installed at $RUSTUP_HOME"
+    echo "Cargo installed at $CARGO_HOME"
+    echo $(cargo --version)
+  '';
+}