MudIcon: Add role="img"

[danielchalmers]

Description

https://developer.mozilla.org/en-US/docs/Web/Accessibility/ARIA/Roles/Img_role#svg_and_roleimg
https://stackoverflow.com/a/4756461
https://stackoverflow.com/questions/49197524/what-is-the-default-aria-role-for-an-svg

(probably) Resolves #3315

How Has This Been Tested?

visually

Type of Changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation (fix or improvement to the website or code docs)

Checklist

• The PR is submitted to the correct branch (dev).
• My code follows the code style of this project.
• I've added relevant tests.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 90.21%. Comparing base (28bc599) to head (39b6b01).
Report is 165 commits behind head on dev.

Additional details and impacted files

@@            Coverage Diff             @@
##              dev    #8915      +/-   ##
==========================================
+ Coverage   89.82%   90.21%   +0.38%     
==========================================
  Files         412      425      +13     
  Lines       11878    12293     +415     
  Branches     2364     2409      +45     
==========================================
+ Hits        10670    11090     +420     
+ Misses        681      670      -11     
- Partials      527      533       +6     

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