Chore: Update README.md

[sean-breen]

Proposed changes

docs: revamp README for user friendliness

• Add tagline, badges, and table of contents for easy navigation
• Add Features section highlighting key capabilities
• Add Quick Start section with Helm and manifest install commands
• Add Docker Images section listing all distribution registries
• Add LTS Releases subsection with registry links
• Consolidate Documentation links into a summary table
• Expand community call dates through October 2026
• Move detailed release matrix and SBOM info into subsections

Checklist

Before creating a PR, run through this checklist and mark each as complete.

• I have read the CONTRIBUTING doc
• I have added tests that prove my fix is effective or that my feature works
• I have checked that all unit tests pass after adding my changes
• I have updated necessary documentation
• I have rebased my branch onto main
• I will ensure my PR is targeting the main branch and pulling from my branch from my own fork

[Copilot]

Pull request overview

This PR revamps README.md to make the NGINX Ingress Controller repository more user-friendly by adding a short product summary, reorganizing sections (Features/Quick Start/Docs/Images/Releases/Community), and consolidating key links into tables.

Changes:

• Adds a new landing structure with tagline, badges, and table of contents.
• Introduces streamlined sections for Features, Quick Start, Documentation, Docker Images, and Releases (including LTS + SBOM info).
• Expands and reorganizes Community information, including community call dates through October 2026.

[javorszky]

One tiny nit I don't actually care about that much.

Broader question: what is the reason for the document reorg? Was there a pain point by someone / someones? Asking more for traceability than anything.