MWPW-159032: Defaults to empty alt tag on the svg - Accessibility requirement

[joaquinrivero]

*This exist before, and we are getting request by accessibility to added again for unity project

• Defaults to empty alt tag on the image if no alt text is authored. Per accessibility best practices this declares the image as "decorative".

Resolves: MWPW-159032
Test URLs:

• Before: https://main--dc--adobecom.hlx.page/acrobat/online/test/sign-pdf-projectunity?martech=off
• After: https://main--dc--adobecom.hlx.page/acrobat/online/test/sign-pdf-projectunity?martech=off&milolibs=MWPW-159032--milo--joaquinrivero

[aem-code-sync]

	Page	Scores	Audits	Google
📱	/acrobat/online/test/sign-pdf-projectunity?martech=off
🖥️	/acrobat/online/test/sign-pdf-projectunity?martech=off
📱	/acrobat/online/test/sign-pdf-projectunity?martech=off&milolibs=MWPW-159032--mil o--joaquinrivero
🖥️	/acrobat/online/test/sign-pdf-projectunity?martech=off&milolibs=MWPW-159032--mil o--joaquinrivero

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 95.96%. Comparing base (5ddeb73) to head (2be5f77).
Report is 39 commits behind head on stage.

Additional details and impacted files

@@            Coverage Diff             @@
##            stage    #2947      +/-   ##
==========================================
- Coverage   96.29%   95.96%   -0.33%     
==========================================
  Files         240      175      -65     
  Lines       54739    46838    -7901     
==========================================
- Hits        52709    44950    -7759     
+ Misses       2030     1888     -142     

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[github-actions]

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[github-actions]

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