feat: Opacity attribute

[marc2332]

To do

• Add docs

[codecov]

Codecov Report

Attention: 26 lines in your changes are missing coverage. Please review.

Comparison is base (b0bb56a) 53.22% compared to head (be037cb) 53.14%.
Report is 1 commits behind head on main.

Files	Patch %	Lines
crates/renderer/src/renderer.rs	0.00%	16 Missing ⚠️
crates/state/src/style.rs	0.00%	6 Missing ⚠️
crates/renderer/src/window.rs	0.00%	4 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #397      +/-   ##
==========================================
- Coverage   53.22%   53.14%   -0.08%     
==========================================
  Files         143      143              
  Lines       12668    12687      +19     
==========================================
  Hits         6742     6742              
- Misses       5926     5945      +19     

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