docs(opacity-checkerboard): enhance README with detailed usage

tools/opacity-checkerboard/README.md

@@ -1,29 +1,108 @@
-## Description
+## Overview
 
-The `opacity-checkerboard` class is used to highlight opacity. Leverage these styles in your component as outlined below to unify you application's visuals with those delivered by various Spectrum Web Components.
+The `opacity-checkerboard` class provides a CSS utility that displays a checkerboard pattern background, commonly used to highlight transparent or semi-transparent areas in UI components. This visual indicator helps users distinguish between transparent and opaque regions, making it an essential tool for color pickers, image editors, and other components that work with opacity.
 
-## Usage
+### Usage
 
-Import the styles from the `opacity-checkerboard` CSS:
+[![See it on NPM!](https://img.shields.io/npm/v/@spectrum-web-components/opacity-checkerboard?style=for-the-badge)](https://www.npmjs.com/package/@spectrum-web-components/opacity-checkerboard)
+[![How big is this package in your project?](https://img.shields.io/bundlephobia/minzip/@spectrum-web-components/opacity-checkerboard?style=for-the-badge)](https://bundlephobia.com/result?p=@spectrum-web-components/opacity-checkerboard)
 
+```bash
+yarn add @spectrum-web-components/opacity-checkerboard
 ```
+
+Import the opacity checkerboard styles from:
+
+```javascript
 import opacityCheckerBoardStyles from '@spectrum-web-components/opacity-checkerboard/src/opacity-checkerboard.css.js';
 ```
 
-Add it to your component's styles array before your component's styles. The order that you include the styles in makes a difference, because selectors within opacity checkerboard may have the same
-specificity as those within your component.
+### Integration
 
-```js
+To integrate the opacity checkerboard styles into your component, add them to your component's styles array. The order of inclusion is important, as selectors within opacity checkerboard may have the same specificity as those within your component:
+
+```javascript
 public static override get styles(): CSSResultArray {
     return [opacityCheckerBoardStyles, styles];
 }
 ```
 
-Use the `opacity-checkerboard` class in your component's `render()` method:
+### Examples
+
+#### Basic usage
+
+Apply the `opacity-checkerboard` class to any element that needs to display the checkerboard pattern:
 
 ```html-live demo
 <div
     class="opacity-checkerboard"
     style="inline-size: 100px; block-size: 100px;"
+    aria-label="Transparency indicator showing checkerboard pattern"
 ></div>
 ```
+
+#### With overlaid content
+
+The opacity checkerboard works well as a background for elements with partial transparency:
+
+```html-live
+<div
+    class="opacity-checkerboard"
+    style="inline-size: 200px; block-size: 200px; position: relative;"
+    role="img"
+    aria-label="Color preview with transparency"
+>
+    <div
+        style="
+            position: absolute;
+            inset: 0;
+            background-color: rgba(255, 0, 0, 0.5);
+        "
+        aria-label="Semi-transparent red color overlay"
+    ></div>
+</div>
+```
+
+### Accessibility
+
+When implementing the opacity checkerboard pattern, ensure proper accessibility by:
+
+- **Providing context**: Add appropriate ARIA labels to describe what the checkerboard pattern represents
+- **Role attribution**: Use `role="img"` when the checkerboard serves as a visual indicator
+- **Descriptive labels**: Include `aria-label` attributes that explain the purpose of the transparency indicator
+- **Alternative text**: When used in color pickers or image editors, provide text alternatives that describe the transparency level
+
+#### Screen reader support
+
+The opacity checkerboard is a purely visual indicator. Always provide alternative text or descriptions for screen reader users:
+
+```html-live
+<div
+    class="opacity-checkerboard"
+    style="inline-size: 100px; block-size: 100px;"
+    aria-label="Checkerboard pattern indicating transparent areas"
+>
+    <span class="visually-hidden">Current opacity: 75%</span>
+</div>
+```
+
+#### Keyboard navigation
+
+When the opacity checkerboard is part of an interactive component, ensure it doesn't interfere with keyboard navigation:
+
+```html-live
+<button
+    class="color-button"
+    aria-label="Select color with 50% opacity"
+    aria-describedby="opacity-description"
+>
+    <span
+        class="opacity-checkerboard"
+        style="inline-size: 40px; block-size: 40px; display: block;"
+    ></span>
+    <span id="opacity-description" class="visually-hidden">
+        Color preview shown over checkerboard pattern indicating 50%
+        transparency
+    </span>
+</button>
+```