docs: add Quick Start section with Docker command

[njg7194]

What

Adds a Quick Start section to the README with a Docker one-liner command.

Why

The current README directs users to external documentation for getting started. Adding a Quick Start section directly in the README allows new users to:

1. Try Jaeger immediately without leaving GitHub
2. Understand the basic setup at a glance
3. Know which ports to use for sending traces

This follows the pattern used by many popular CNCF projects (like Prometheus, Grafana) that include quick start commands in their READMEs.

Changes

• Added "Quick Start" section after the Jaeger v2 announcement
• Included Docker command for running Jaeger all-in-one
• Documented common ports (16686 for UI, 4317/4318 for OTLP)
• Added "Architecture" header before the existing mermaid diagram for better structure
• Linked to the full Getting Started guide for production deployments

Testing

Verified the Docker command works:

docker run --rm jaegertracing/jaeger:latest

[dosubot]

Related Documentation

No published documentation to review for changes on this repository.

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.56%. Comparing base (39b645c) to head (454e27b).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #7945      +/-   ##
==========================================
- Coverage   95.57%   95.56%   -0.02%     
==========================================
  Files         316      316              
  Lines       16726    16726              
==========================================
- Hits        15986    15984       -2     
- Misses        577      579       +2     
  Partials      163      163              

Flag	Coverage Δ
badger_v1	9.11% <ø> (ø)
badger_v2	1.90% <ø> (ø)
cassandra-4.x-v1-manual	13.41% <ø> (ø)
cassandra-4.x-v2-auto	1.89% <ø> (ø)
cassandra-4.x-v2-manual	1.89% <ø> (ø)
cassandra-5.x-v1-manual	13.41% <ø> (ø)
cassandra-5.x-v2-auto	1.89% <ø> (ø)
cassandra-5.x-v2-manual	1.89% <ø> (ø)
clickhouse	1.98% <ø> (ø)
elasticsearch-6.x-v1	17.27% <ø> (ø)
elasticsearch-7.x-v1	17.30% <ø> (ø)
elasticsearch-8.x-v1	17.45% <ø> (ø)
elasticsearch-8.x-v2	1.90% <ø> (ø)
elasticsearch-9.x-v2	1.90% <ø> (ø)
grpc_v1	8.44% <ø> (ø)
grpc_v2	1.90% <ø> (ø)
kafka-3.x-v2	1.90% <ø> (ø)
memory_v2	1.90% <ø> (ø)
opensearch-1.x-v1	17.34% <ø> (ø)
opensearch-2.x-v1	17.34% <ø> (ø)
opensearch-2.x-v2	1.90% <ø> (ø)
opensearch-3.x-v2	1.90% <ø> (ø)
query	1.90% <ø> (ø)
tailsampling-processor	0.54% <ø> (ø)
unittests	94.24% <ø> (-0.02%)	⬇️

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[github-actions]

Metrics Comparison Summary

Total changes across all snapshots: 0

Detailed changes per snapshot

summary_metrics_snapshot_cassandra

📊 Metrics Diff Summary

Total Changes: 0

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• 🚫 Excluded: 106 metrics

summary_metrics_snapshot_cassandra

📊 Metrics Diff Summary

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summary_metrics_snapshot_cassandra

📊 Metrics Diff Summary

Total Changes: 0

• 🆕 Added: 0 metrics
• ❌ Removed: 0 metrics
• 🔄 Modified: 0 metrics
• 🚫 Excluded: 53 metrics

summary_metrics_snapshot_cassandra

📊 Metrics Diff Summary

Total Changes: 0

• 🆕 Added: 0 metrics
• ❌ Removed: 0 metrics
• 🔄 Modified: 0 metrics
• 🚫 Excluded: 106 metrics

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