[Feature] AssetsManager methods

[titouanmathis]

This PR adds 2 methods to easily enqueue assets:

$assets_manager->enqueue_style( 'custom-login-css', 'css/admin/custom-login.css' );
$assets_manager->enqueue_script( 'custom-login-js', 'css/admin/custom-login.js' );

To-do

• Add tests
• Update docs

[codecov]

Codecov Report

Attention: Patch coverage is 90.00000% with 2 lines in your changes are missing coverage. Please review.

Project coverage is 67.40%. Comparing base (45d8172) to head (0d61749).
Report is 2 commits behind head on develop.

Files	Patch %	Lines
src/Managers/AssetsManager.php	89.47%	2 Missing ⚠️

Additional details and impacted files

@@              Coverage Diff              @@
##             develop      #23      +/-   ##
=============================================
+ Coverage      66.87%   67.40%   +0.53%     
- Complexity       179      182       +3     
=============================================
  Files             12       12              
  Lines            489      497       +8     
=============================================
+ Hits             327      335       +8     
  Misses           162      162              

Flag	Coverage Δ
unittests	67.40% <90.00%> (+0.53%)	⬆️

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