feat(example): added one

example/Makefile.dart

@@ -0,0 +1,93 @@
+import 'package:drun/drun.dart';
+
+/// Start off by redirecting your main method to the drun method
+Future<void> main(argv) async => drun(argv);
+
+/// Then just create functions that can be called via the command line
+/// call me like: `drun my-task`
+///
+/// HINT: docblocks are used to generate help text on the command line.
+/// try `drun my-task --help`
+void myTask() {
+  print('Mello World');
+}
+
+/// Both sync and async functions are supported
+/// call me like: `drun my-async-task`
+Future<void> myAsyncTask() async {
+  await Future.delayed(Duration(seconds: 3));
+  print('Mello World');
+}
+
+/// Private functions do not get exposed as CLI tasks.
+/// The same is true for anything that is imported or exported,
+/// regardless of their visibility.
+///
+/// Only public functions in your "Makefile.dart" will be considered as tasks
+void _myPrivateTask() {}
+
+/// Tasks can have parameters.
+/// call me like: `drun my-task-with-parameter --foo-bar abc123`
+///
+/// * [fooBar] Parameters may optionally be documented like this.
+///   Multiple lines are allowed.
+///
+///   Parameters can be of the following types: bool, int, double, String
+///   List<int>, List<double>, List<String>
+void myTaskWithParameter(String fooBar) {
+  print('fooBar=${fooBar}');
+}
+
+/// Tasks can have parameters with default values.
+///
+/// NOTE: Optional parameters are supported, named parameters are not!
+void myTaskWithParameterDefault([String fooBar = 'abc123']) {
+  print('fooBar=${fooBar}');
+}
+
+/// Tasks can have have flags (as opposed to cli options).
+///
+/// Boolean flags do not accept values, they are either present donoting true
+/// or they are absent denoting false.
+///
+/// call me like: `drun my-task-with-bool-flag --debug-mode`
+void myTaskWithBoolFlag(bool debugMode) {
+  print('debugMode=${debugMode}');
+}
+
+/// Tasks can have paramters that are lists.
+///
+/// These are represented as CSV strings on the command line.
+/// Only List<int>, List<double>, List<String> is currenty supported.
+///
+/// call me like: `drun my-task-with-csv-list --numbers "1,2,3,4,5,6,7,8,9"`
+void myTaskWithCsvList(List<int> numbers) {
+  print('numbers=${numbers}');
+}
+
+/// Parameters can be abbreviated.
+/// call me like: `drun my-task-with-abbreviated-parameter -f abc123`
+void myTaskWithAbbreviatedParameter(@Abbr('f') String foobar) {
+  print('foobar=${foobar}');
+}
+
+/// Parameters can get their values from the environment.
+/// call me like: `FOO_BAR=abc123 drun my-task-with-env-parameter`
+///
+/// A CLI option will always take precedence over an environment variable.
+void myTaskWithEnvParameter(@Env('FOO_BAR') String foobar) {
+  print('foobar=${foobar}');
+}
+
+/// Parameters can be restricted to specfic set of values.
+///
+/// These calls are valid:
+/// * `drun my-task-with-value-validation --foobar foo`
+/// * `drun my-task-with-value-validation --foobar bar`
+///
+/// These calls are invalid:
+/// * `drun my-task-with-value-validation --foobar abc`
+/// * `drun my-task-with-value-validation --foobar xyz`
+void myTaskWithValueValidation(@Values(['foo', 'bar']) String foobar) {
+  print('foobar=${foobar}');
+}