Document Android adaptive icon build hints

[shai-almog]

Motivation

• Add documentation for new Android adaptive icon build hints so projects can opt into adaptive launcher icons and configure their background via build hints.

Description

• Introduce three build hint entries: android.enableAdaptiveIcons which enables adaptive icon generation and causes Codename One to generate mipmap launcher resources (ic_launcher, ic_launcher_foreground, and adaptive XML in mipmap-anydpi-v26) and update the manifest android:icon and android:roundIcon, android.adaptiveIconBackground which sets the background color (defaults to #ffffff and is written as @color/ic_launcher_background), and android.adaptiveIconBackgroundImage which accepts a path relative to the native Android project and, when set, overrides the background color.

Testing

• Built the documentation with asciidoctor to validate formatting and ensure the new entries render correctly, and the build completed successfully.

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Codex Task

[github-actions]

Developer Guide build artifacts are available for download from this workflow run:

• Developer Guide HTML package
• Developer Guide PDF
• AsciiDoc linter report
• Vale report
• Unused image report

Developer Guide quality checks:

• AsciiDoc linter: No issues found (report)
• Vale: 18803 alert(s) (2767 errors, 6378 warnings, 9658 suggestions) (exit code 1) (report)
• Image references: No unused images detected (report)