docs: update docs

.gitignore

@@ -8,3 +8,4 @@ build/
 ios/.generated/
 ios/Flutter/Generated.xcconfig
 ios/Runner/GeneratedPluginRegistrant.*
+doc/

README.md

@@ -1,8 +1,29 @@
 # wheel_spinner
 
-WheelSpinner provides you with a simple number spinner that resembles a wheel, knob, or more specifically
-pitch bender knobs. It allows you to update a single `double` value.
+WheelSpinner provides you with a simple number spinner that resembles a wheel, knob, or more
+specifically pitch bender knobs. It allows you to update a single `double` value with a finger fling
+or drag as in the example below.
 
-## Getting Started
+<img src="https://casraf.blog/assets/images/wheel-spinner-tutorial/scr04.gif" width="300px" />
+<img src="https://casraf.blog/assets/images/wheel-spinner-tutorial/scr05.gif" width="300px" />
 
-- TODO
+## How to use
+
+Simply import the package, and use the exposed `WheelSpinner` widget.
+
+See all the individual parameters for more details on theme and display customization, as well as
+event handlers. Here is a simple usage example:
+
+```dart
+Widget build(BuildContext context) {
+  return WheelSpinner(
+    value: value,
+    width: width,
+    min: 0.0,
+    max: 100.0,
+    borderRadius: borderRadius,
+    minMaxLabelBuilder: (value) => value,
+    onSlideUpdate: (val) => onChange(value),
+  );
+}
+```

lib/utils.dart

@@ -1,5 +1,5 @@
 import 'dart:math';
 
-/// clamps [value] to [min] and [max]
+/// clamps [number] to [low] and [high]
 double clamp<T extends num>(T number, T low, T high) =>
     max(low * 1.0, min(number * 1.0, high * 1.0));

lib/wheel_spinner.dart

@@ -1,3 +1,4 @@
+/// The main library for the wheel spinner.
 library wheel_spinner;
 
 import 'package:flutter/material.dart';