Generate README.md and README.fr.md from a single README.src.md (NRG)

[andriishin]

Bonjour ! 👋 / Hi! This PR migrates README.md and README.fr.md to a single README.src.md template; both files are then regenerated by Nanolaba Readme Generator (NRG) during mvn compile.

Why / Pourquoi

Maintaining two parallel READMEs drifts over time. A single source of truth keeps them in lockstep — and it's a small change since the existing files already follow NRG's <base>.md / <base>.<lang>.md naming convention, no rename needed.

What changed / Ce qui change

• New README.src.md (~37 lines) — single template covering both languages. Identical content (logo, badges, headings) appears once; per-language strings use the inline ${en:'…', fr:'…'} form. The Setup subsection lives in the EN file only (matching current behaviour where README.fr.md links back to the EN #Setup anchor).
• Modified pom.xml — adds com.nanolaba:nrg-maven-plugin:1.0 (≈22-line <plugin> block at the end of the parent <build><plugins>). Default phase is compile, no extra config. Multi-module: the plugin runs once at the parent level, no per-module setup needed.
• Modified README.md and README.fr.md — regenerated from the template; the only semantic change is a 2-line NRG-added header (<!-- This file was automatically generated by NRG 1.0 -->) so future contributors know to edit README.src.md instead. Body content is byte-identical to the current files.

How to verify / Vérification

1. Run mvn compile (or ./mvnw compile if applicable) — NRG will regenerate both READMEs from README.src.md.
2. git diff should be empty.
3. To change a string in the README in the future, edit only README.src.md.

What NRG is

NRG is an Apache 2.0, Java 8 Markdown template engine purpose-built for multi-language READMEs. Distributed as a CLI, Maven plugin (already on Maven Central as com.nanolaba:nrg-maven-plugin:1.0), and Java library. Used to generate its own README from README.src.md.

If the migration angle doesn't fit Eno's direction, no problem — feel free to close. Happy to adjust the template (e.g. switch the inline form to per-line <!--lang--> markers, or split the Setup section). 🙇