Add README for Analytics & Visualization SIG

[Copilot]

The repository lacked documentation explaining the purpose and scope of the Analytics & Visualization Special Interest Group.

Changes

• Added comprehensive README.md covering:
  • SIG purpose: community of practice for data analytics and visualization at Netherlands eScience Center
  • Topics covered: data analytics (ML, big data), visualization technologies (D3.js, Plotly, Matplotlib), visualization methods, interactive dashboards, best practices, emerging trends (AI, VR/AR)
  • Participation details: open to eScience Center staff and collaborators
  • Resources and license information

The README provides clear context for the SIG's focus areas and how members can engage.

Original prompt

This is a special interest group at the eScience Center. We will be taclking topics surrounding analytics and visualization technologies, methods, techniques. Please make a short but informed readme

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