Add experimental code generator

See https://github.com/flutter/flutter/wiki/Code-generation-in-Flutter

- Generates a .dart widget class based on a .json file

Author: maru

README.md

@@ -4,6 +4,34 @@
 
 # NStack Flutter
 
-NStack Flutter, provided as a Plugin Package, is the companion software development kit to the [NStack](https://nstack.io) backend.
+[NStack] Flutter, provided as a plugin package, is a companion software development kit to the [NStack](https://nstack.io) backend.
 
-See [NStack documentation](https://nstack-io.github.io/docs/docs/guides/flutter/flutter.html) for more information.
+See [NStack documentation](https://nstack-io.github.io/docs/docs/guides/flutter/flutter.html) for more information.
+
+# How to use
+
+## Install
+
+To use [NStack], you will need your typical [build_runner]/code-generator setup.\
+First, install [build_runner] and [NStack] by adding them to your `pubspec.yaml` file:
+
+```yaml
+# pubspec.yaml
+dependencies:
+  nstack:
+
+dev_dependencies:
+  build_runner:
+```
+
+This installs two packages:
+
+- build_runner, the tool to run code-generators
+- [NStack] SDK, which includes a code generator
+
+## Run the generator
+
+Depending on your use case you have two possibilities:
+
+- `flutter pub pub run build_runner build`, if your package depends on Flutter
+- `pub run build_runner build` otherwise

build.yaml

@@ -0,0 +1,20 @@
+# Read about `build.yaml` at https://pub.dartlang.org/packages/build_config
+targets:
+  $default:
+    builders:
+      freezed:
+        enabled: true
+        generate_for:
+          exclude:
+            - test
+            - example
+          include:
+            - test
+
+builders:
+  jsonWidgetBuilder:
+    import: "package:nstack/json_widget.dart"
+    builder_factories: ["jsonWidgetBuilder"]
+    build_extensions: {".json": [".dart"]}
+    build_to: source
+    auto_apply: dependents

example/lib/example.json

@@ -0,0 +1,12 @@
+{
+  "name": "Container",
+  "params": {
+    "color": "#Color(0xFF22DD11)",
+    "child": {
+      "name": "Text",
+      "params": {
+        "0": "Hello, World"
+      }
+    }
+  }
+}