normalize idl name when matching asset

[panva]

the convention where a name matches exactly no longer holds since web-platform-tests/wpt#52264

[panva]

Actually, even the name lowercased name doesn't hold anymore... gotta think of something else.

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 1 line in your changes missing coverage. Please review.

Project coverage is 79.76%. Comparing base (404c0ac) to head (db6ed55).

Files with missing lines	Patch %	Lines
lib/wpt/index.js	0.00%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #926   +/-   ##
=======================================
  Coverage   79.76%   79.76%           
=======================================
  Files          39       39           
  Lines        4630     4630           
=======================================
  Hits         3693     3693           
  Misses        937      937           

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