Enhance README.md: Improve formatting, accessibility, and clarity

[akshith30388]

This pull request improves the README.md file for better readability and usability. Changes include:

• Added a project title at the top (# OpenSearch) and included alt text for the logo for accessibility.
• Grouped badges with horizontal rules for better visual separation.
• Added a "Table of Contents" heading for clarity.
• Improved spacing and formatting for headers and lists.
• Expanded the Welcome section with a short, clear introduction.
• Minor corrections: LinkedIn badge capitalization and consistent Markdown formatting.

[github-actions]

❌ Gradle check result for 3221498: FAILURE

Please examine the workflow log, locate, and copy-paste the failure(s) below, then iterate to green. Is the failure a flaky test unrelated to your change?

[sandeshkr419]

Thanks @akshith30388 for spending efforts improving this.

Did you somehow changed the file name extension - README.md to README.md.save? It is showing as a new file and I'm not able to see what did you actually change.
Can you please fix the file name, so that the changes can be viewed?

[github-actions]

✅ Gradle check result for 3e2af78: SUCCESS

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 73.14%. Comparing base (133e9d9) to head (3e2af78).
⚠️ Report is 5 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff              @@
##               main   #19716      +/-   ##
============================================
+ Coverage     73.11%   73.14%   +0.03%     
+ Complexity    70838    70814      -24     
============================================
  Files          5732     5732              
  Lines        324191   324246      +55     
  Branches      46922    46923       +1     
============================================
+ Hits         237017   237180     +163     
+ Misses        68068    67882     -186     
- Partials      19106    19184      +78     

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[github-actions]

❌ Gradle check result for aa69431: FAILURE

Please examine the workflow log, locate, and copy-paste the failure(s) below, then iterate to green. Is the failure a flaky test unrelated to your change?

[github-actions]

❌ Gradle check result for f4367e0: null

Please examine the workflow log, locate, and copy-paste the failure(s) below, then iterate to green. Is the failure a flaky test unrelated to your change?

[opensearch-trigger-bot]

This PR is stalled because it has been open for 30 days with no activity.