Add YAJL migration analysis and library snapshots (EN/DE)

[Easton97-Jens]

Motivation

• Provide a factual analysis to evaluate removing YAJL (Issue Drop YAJL dependency owasp-modsecurity/ModSecurity#3308) by collecting repository metadata and comparing alternative JSON libraries.
• Capture observable signals about maintenance, CVEs, packaging, and migration risks to support a project decision.

Description

• Add analysis/library_snapshot.txt containing GitHub metadata snapshots for YAJL, JSON-C, Jansson, and RapidJSON.
• Add analysis/library_tags.txt containing observed release tags and dates for the same libraries.
• Add detailed migration analysis documents analysis/yajl-migration-analysis.en.md and analysis/yajl-migration-analysis.de.md that compare YAJL to json-c/json-c, akheron/jansson, and Tencent/rapidjson, summarize risks, and provide a recommendation.

Testing

• No automated tests were added or modified for these documentation/analysis files.
• No CI or unit tests were executed as part of this documentation-only change.
• Existing CI pipelines should be unaffected by these additions.

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Codex Task