Fix regex to match async and defer attributes

[jamieburchell]

Fixes #1226

[codecov-commenter]

Codecov Report

❌ Patch coverage is 0% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 1.53%. Comparing base (e60b718) to head (a24d368).

Files with missing lines	Patch %	Lines
Minify_AutoJs.php	0.00%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff            @@
##             master   #1227   +/-   ##
========================================
  Coverage      1.53%   1.53%           
  Complexity    19575   19575           
========================================
  Files           634     634           
  Lines         98522   98522           
========================================
  Hits           1509    1509           
  Misses        97013   97013           

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