fix(svg): mention xmlwriter extension in error message

[DASPRiD]

Closes #182

[codecov]

Codecov Report

❌ Patch coverage is 0% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 71.79%. Comparing base (bf7d67c) to head (3e656f4).
⚠️ Report is 3 commits behind head on main.

Files with missing lines	Patch %	Lines
src/Renderer/Image/SvgImageBackEnd.php	0.00%	2 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##               main     #232      +/-   ##
============================================
- Coverage     71.81%   71.79%   -0.03%     
  Complexity      995      995              
============================================
  Files            49       49              
  Lines          3151     3152       +1     
============================================
  Hits           2263     2263              
- Misses          888      889       +1     

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