Update README for PowerToys 0.102 #51396

Summary of the Pull Request

Updates the README for the PowerToys 0.102 release by:

• Replacing the What's new banner with the 0.102 release artwork


• Updating the roadmap for v0.103: a new Awake flyout, Screen Ruler improvements, and continued WinUI 3 modernization of utilities

PR Checklist

• [ ] Closes: #xxx
  <!-- - [ ] Closes: #yyy (add separate lines for additional resolved issues) -->


• [x] Communication: I've discussed this with core contributors already. If the work hasn't been agreed, this work might be rejected


• [ ] Tests: Added/updated and all pass


• [ ] Localization: All end-user-facing strings can be localized


• [ ] Dev docs: Added/updated


• [ ] New binaries: Added on the required places
  
  
  • [ ] JSON for signing for new binaries
  
  
  • [ ] WXS for installer for new binaries and localization folder
  
  
  • [ ] YML for CI pipeline for new test projects
  
  
  • [ ] YML for signed pipeline
    
  
  
  
  


• [ ] Documentation updated: If checked, please file a pull request on our docs repo and link it here: #xxx

Detailed Description of the Pull Request / Additional comments

doc/images/readme/Release-Banner.png is replaced with the supplied 1200×252 PowerToys 0.102 artwork (same dimensions as the previous banner). The roadmap now links to the PowerToys 0.103 milestone. The utilities table is unchanged because the new Mouse Button Lock and CursorHide utilities are part of Mouse Utilities.

Validation Steps Performed

• 
  Get-FileHash comparison: the committed banner matches the supplied image exactly (passed); dimensions confirmed at 1200×252


• 
  Invoke-WebRequest -Method Head https://github.com/microsoft/PowerToys/milestone/47: returned 200 (passed)


• 
  git diff --check: no whitespace errors (passed)

Documentation and image-only change; automated tests are not applicable.