feat: made some translations for getting started and quickstart

[kayiganwa04]

Summary

Adds and wires French (/fr/) documentation for getting started, quickstarts, adoption, and product features, and updates VuePress (config, enhanceApp, 404, theme utilities) so the French site and navigation behave correctly.

Details

• Content: New/updated French pages under docs/fr/ (getting started, demos, FAQs, installation, license, quickstarts; adoption and product sections with diagrams/assets where needed).
• Site: Locale-aware routing/redirects and a 404 layout that does not hard-code a single language.
• Developer experience: scripts/_build_plantuml.sh exits early when no staged .puml/.plantuml files are present, so pre-commit does not require Docker for unrelated doc commits.
• Dependencies: package.json / lockfile updates aligned with the build.

Testing

pnpm / npm build (and local preview) for the docs site; commit hooks with only non–PlantUML changes succeed without Docker.

[MaximeNzo]

Nice PR @kayiganwa04