feat(layout): add Offset::new() constructor

[joshka]

No description provided.

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 3 lines in your changes missing coverage. Please review.

Project coverage is 93.0%. Comparing base (18e70d3) to head (57a041b).
Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
ratatui-core/src/layout/rect.rs	0.0%	3 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##            main   #1547     +/-   ##
=======================================
- Coverage   93.0%   93.0%   -0.1%     
=======================================
  Files         72      72             
  Lines      16838   16841      +3     
=======================================
  Hits       15664   15664             
- Misses      1174    1177      +3     

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