fix: xhr string request body can specify Content-Type

[monkeyWie]

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 59.85%. Comparing base (4294d07) to head (3b1aebc). Report is 33 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #596      +/-   ##
==========================================
- Coverage   59.94%   59.85%   -0.09%     
==========================================
  Files          19       19              
  Lines        3008     3044      +36     
==========================================
+ Hits         1803     1822      +19     
- Misses       1008     1022      +14     
- Partials      197      200       +3     

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.