Editorial: clarify OS is backing store

[marcoscaceres]

Closes #113

This pull request clarifies how badge values are managed for installed web applications in the index.html documentation. Specifically, it explains that the operating system is responsible for storing and managing the badge value, with the user agent serving as an intermediary to communicate changes.

Documentation clarification:

• Updated the description of badge initialization to state that the operating system manages the badge value and the user agent communicates badge changes to the OS.

This change:

• Makes editorial changes (changes informative sections, or changes normative sections without changing behavior)

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[Copilot]

Pull Request Overview

This PR clarifies the documentation for badge value management in installed web applications, specifically explaining the role of the operating system as the backing store for badge values.

• Adds clarification that the operating system stores and manages badge values
• Explains the user agent's role as an intermediary between the application and OS
• Makes editorial improvements to the badge initialization documentation

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[fallaciousreasoning]

lgtm