docs: refresh the README

[roxblnfk]

🔍 What was changed

• New README header: centered RoadRunner logo, tagline and short description; installation block with shields.io badges (PHP, version, license, downloads). No quality badges: the repo runs no Psalm, coverage or mutation testing.
• The plugin list matches the generated RoadRunner\ namespaces (App Logger and Temporal added, the removed Plugins dropped), plus a note on the Temporal API / Temporal Cloud API messages and their google/common-protos requirement.
• Generation notes updated: protoc v34 as pinned by CI, and the submodule init step. The License section is removed.

[coderabbitai]

Important

• 🔍 Trigger review

This repository does not receive automatic reviews because it has fewer than 10 stars.

⚙️ Run configuration

• Configuration used: defaults
• Review profile: CHILL
• Plan: Advanced
• Run ID: f26588c3-25da-4f13-b15a-1a5cb27457c4

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