[mqtt.awtrix3] Parse font tags for multi-colored app texts

[DrRSatzteil]

This PR adds text parsing for the text channel. You may use html-style tags like these RED to color only parts of your app text. The color channel defines the default color and text effects as well as gradient colors will be ignored when font tags are used.

[Copilot]

Pull Request Overview

This PR implements font color tag parsing for the MQTT Awtrix3 binding, allowing users to display text with multiple colors using HTML-style font tags. When font tags are detected in the text, the implementation switches from using simple text to a structured text segment array where each segment has its own color.

Key changes:

• Added text parsing logic to detect and process <font color="#RRGGBB">text</font> tags
• Modified text processing to conditionally apply text effects only when font tags are not present
• Added comprehensive test coverage for various font tag scenarios

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 3 comments.

File	Description
AwtrixApp.java	Implements font tag parsing logic with TextSegment class and conditional text effect handling
AwtrixAppTest.java	Adds comprehensive test coverage for font tag parsing scenarios
README.md	Documents the new font color tag feature with syntax, examples, and usage notes

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[lsiepel]

Thanks LGTM