new(nix): Added flake-based devshell setup leveraging your own flake / overlay

.envrc

@@ -0,0 +1 @@
+use flake

.gitignore

@@ -31,3 +31,4 @@
 /classes
 /target
 .garden/
+.direnv

flake.nix

@@ -0,0 +1,29 @@
+{
+  description = "A Nix-flake-based development environment for application.garden";
+
+  inputs = {
+    nixpkgs.url = "github:NixOS/nixpkgs/nixpkgs-unstable";
+    garden.url = "github:nextjournal/garden-cli";
+  };
+
+  outputs = { self, nixpkgs, garden }:
+    let
+      # Latest LTS releases as of Nov 2023
+      javaVersion = 21;
+      supportedSystems = [ "x86_64-linux" "aarch64-linux" "x86_64-darwin" "aarch64-darwin" ];
+      forEachSupportedSystem = f: nixpkgs.lib.genAttrs supportedSystems (system: f {
+        pkgs = import nixpkgs {
+          inherit system;
+          overlays = [
+            garden.overlays.default
+          ];
+        };
+      });
+    in {
+      devShells = forEachSupportedSystem ({ pkgs }: {
+        default = pkgs.mkShell {
+            buildInputs = [ pkgs.clojure pkgs.garden ];
+          };
+      });
+    };
+}