[CONTENT-3798] README update for marketing

[tom-howlett-sonarsource]

Summary

This PR makes a focused README marketing update:

• adds the responsive Sonar logo and a clear SonarJava heading
• refreshes the opening description and adds useful repository/community badges
• adds concise context showing where SonarJava is available across the SonarQube product family

The repository's existing feature counts, documentation links, build and test instructions, support and contribution guidance, and licensing are otherwise preserved.

Review guidance

These changes were prepared automatically using the shared README guidelines.

Please review the diff carefully for repository-specific and product-marketing accuracy, verify the logo in GitHub light and dark modes, and confirm that all required checks pass.

Merge ownership

If the changes are accurate and all required checks pass, please have a CODEOWNER merge this PR when you are ready. The rollout author will not merge it because the repository owners are best placed to assess repository-specific checks and any build impact.

If a check fails or a correction is needed, please leave the PR unmerged and add a review comment.

Validation

• reconciled with master at 4143700b3bdf9e3888aac0cf1e48b39e3d84e6fa
• confirmed that feature counts, technical documentation, build and test commands, support and contribution guidance, and licence text remain unchanged
• verified the new links and CDN-hosted light/dark logo URLs
• deliberately excluded the earlier proposed quickstart, FAQ, and technical or policy rewrites

This is a documentation-only change and does not modify runtime code.

Tracking

Jira epic: CONTENT-3798

[hashicorp-vault-sonar-prod]

CONTENT-3798

[gitar-bot]

Code Review ✅ Approved

README marketing update adds responsive Sonar logo, SonarJava heading, refreshed opening description, and repository/community badges while preserving existing feature counts, documentation links, build/test instructions, and contribution guidance. No issues found.

Implementation Status ✅ 1 of 1 objectives covered

✅ CONTENT-3798 - 1 of 1 objectives covered

This PR updates the public GitHub README with the new Sonar logo and messaging.

✅ 1 covered here

• ✅ Update public GitHub READMEs with the Sonar logo and messaging

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[sonarqube-next]

Quality Gate passed

Issues
0 New issues
0 Fixed issues
0 Accepted issues

Measures
0 Security Hotspots
0 Dependency risks
No data about Coverage
No data about Duplication

See analysis details on SonarQube

[mary-georgiou]

LGTM