Update El Salvador holidays, add l10n support

[KJhellico]

Proposed change

Update El Salvador holidays, add l10n support (en_US, es, uk).

Type of change

• New country/market holidays support (thank you!)
• Supported country/market holidays update (calendar discrepancy fix, localization)
• Existing code/documentation/test/process quality improvement (best practice, cleanup, refactoring, optimization)
• Dependency update (version deprecation/pin/upgrade)
• Bugfix (non-breaking change which fixes an issue)
• Breaking change (a code change causing existing functionality to break)
• New feature (new holidays functionality in general)

Checklist

• I've followed the contributing guidelines
• I've successfully run make check, all checks and tests are green

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 100.00%. Comparing base (16e6f17) to head (7d3c4d2).
Report is 2 commits behind head on dev.

Additional details and impacted files

@@            Coverage Diff            @@
##               dev     #2209   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files          195       195           
  Lines        11762     11768    +6     
  Branches      1699      1699           
=========================================
+ Hits         11762     11768    +6     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[arkid15r]

LGTM 👍

[PPsyrius]

LGTM 🇸🇻