Fix Accessibility Violations - Add Accessible Labels to Copy Buttons

[huangkevin-apr]

Summary

This PR fixes accessibility violations in the Quick Install section where copy-to-clipboard buttons lack accessible labels, making them unusable for screen reader users.

Why is this important?
Associating a meaningful label with every UI control allows the browser and assistive technology to expose and announce the control to a user. Associating a visible label also provides a larger clickable area.

Problems Identified

The IBM Equal Access Accessibility Checker identified critical violations:

Issue 1: npm install Command Copy Button

• Violation: Form control element <button> has no associated label
• Element: Copy button for npm install rescript command
• Impact: Screen reader users cannot identify the button's purpose or what content will be copied

Issue 2: npx create Command Copy Button

• Violation: Form control element <button> has no associated label
• Element: Copy button for npx create-rescript-app command
• Impact: Screen reader users cannot identify the button's purpose or what content will be copied

Solution

Added a descriptive ariaLabel prop to the copy button that dynamically includes the command being copied:

ariaLabel={"Copy " ++ code ++ " command"}

Testing

• Validated with IBM Equal Access Accessibility Checker - both violations resolved
• Tested with screen readers (NVDA/JAWS) to confirm proper label announcement
• Verified labels are correctly generated for both commands

Fix Before:

**Fix After:""