Properly handle margin-left and margin-right specified on the input elements.

[dpvc]

This PR fixes the output jax to take margin css into account when positioning elements and computing their widths. The code already handles padding and border CSS, so this adds similar support for margin. This is needed in order to support the next PR to work around a bug in Safari that affects bussproof layouts.

[codecov]

Codecov Report

❌ Patch coverage is 11.42857% with 31 lines in your changes missing coverage. Please review.
✅ Project coverage is 86.42%. Comparing base (da21770) to head (e4cb499).
⚠️ Report is 3 commits behind head on develop.

Files with missing lines	Patch %	Lines
ts/output/common/Wrapper.ts	13.04%	20 Missing ⚠️
ts/output/svg/Wrapper.ts	8.33%	11 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #1456      +/-   ##
===========================================
- Coverage    86.45%   86.42%   -0.03%     
===========================================
  Files          340      340              
  Lines        86106    86133      +27     
  Branches      3191     4836    +1645     
===========================================
+ Hits         74439    74442       +3     
- Misses       11667    11691      +24     

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