feat(module:avatar): add loading and fetchpriority attributes

[arturovt]

Closes #7274

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 92.05%. Comparing base (42bbb0c) to head (8d89f6f).
Report is 9 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #7347      +/-   ##
==========================================
+ Coverage   91.99%   92.05%   +0.06%     
==========================================
  Files         560      560              
  Lines       19617    19609       -8     
  Branches     3095     3095              
==========================================
+ Hits        18047    18052       +5     
+ Misses       1233     1218      -15     
- Partials      337      339       +2     

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

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.

[simplejason]

As caniuse->loading and caniuse->fetchpriority shown, these attributes have low compatibility for most browsers, I don't think we need built-in properties to support. What do you think about this @hsuanxyz ?

[Laffery]

Could you please update the document about these new inputs and add test cases if possible?

[Laffery]

LGTM

[HyperLife1119]

LGTM