fix: Add example file with CAWG X.509 signing

[scouten-adobe]

This PR adds a new C2PA example asset (JPEG in this case) with a C2PA claim signer signature and a CAWG identity assertion with its own X.509 signature from a different credential holder.

It includes the code that was used to generate the asset as an example.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 78.78%. Comparing base (85f97b5) to head (a2d5454).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #948      +/-   ##
==========================================
- Coverage   78.80%   78.78%   -0.02%     
==========================================
  Files         146      146              
  Lines       35096    35096              
==========================================
- Hits        27657    27652       -5     
- Misses       7439     7444       +5     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.