feat: impl Widget for &str and String

[kdheepak]

Currently, f.render_widget("hello world".bold(), area) works but f.render_widget("hello world", area) doesn't. This PR changes that my implementing Widget for &str and String. This makes it easier to render strings with no styles as widgets.

Example usage:

terminal.draw(|f| f.render_widget("Hello World!", f.size()))?;

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (11b452d) 91.9% compared to head (d430470) 91.9%.

Additional details and impacted files

@@          Coverage Diff          @@
##            main    #952   +/-   ##
=====================================
  Coverage   91.9%   91.9%           
=====================================
  Files         61      61           
  Lines      15703   15723   +20     
=====================================
+ Hits       14436   14456   +20     
  Misses      1267    1267           

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[joshka]

Tests and docs needed.

[joshka]

Need to add some sort of comment to the Widget trait or widget module for this.

[orhun]

LGTM