docs(article): DEV Community向け英語紹介記事を準備する

[hideyukiMORI]

Purpose

Prepare the first English introduction article for DEV Community.

Scope

• Explain NeNe as a tiny renovated legacy-style PHP framework.
• Emphasize explicit conventions, reviewability, REST/OpenAPI/tests, and the fact that NeNe is not a Laravel/Symfony competitor.
• Link to GitHub, demo, release, and tutorial.

Acceptance criteria

• The article can be published or copied to DEV Community with minimal edits.
• The article invites feedback without sounding promotional.