docs: add draft FAQ page and enable link

[elharo]

• Creates new src/site/xdoc/faq.xml with basic structure
• Uncomments FAQ navigation item in site.xml

Fixes #3.

[gnodet]

The idea of adding a FAQ page is welcome, but the current content has a factual error and formatting inconsistencies:

Verified issues:

1. Factual error (high): The FAQ states "Maven 4.x requires Java 8 or later" but the project's pom.xml defines <javaVersion>17</javaVersion> — Maven 4.x requires Java 17, not Java 8. This would give users incorrect information.
2. License header format (medium): The ASF license header is on a single line, while the existing xdoc file (index.xml) uses the standard multi-line format. This is inconsistent with the project's established convention.
3. Wrong issue reference (low): The PR body says "Fixes #3" but issue #3 is "Reverting some unexpected aether dependency changes to the top-level pom" — an unrelated, already-closed issue. Merging would incorrectly reference that issue.

Please fix the Java version requirement to Java 17 and reformat the license header to match the multi-line format used in src/site/xdoc/index.xml.

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Claude Code on behalf of gnodet

[slawekjaranowski]

Maven 4.x requires Java 8
😄 ?

[slawekjaranowski]

I would like to managed such FAQ at docs site somewhere: https://maven.apache.org/index.html

We have in many places FAQ which is outdated ... I afraid that this will be also outdated soon 😄