Add String::isEmpty()

[alranel]

This PR adds a tiny inline isEmpty() method to the String class. This is borrowed from the ESP32 core which made it popular.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (65633ce) 95.53% compared to head (2e5570e) 95.53%.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #220   +/-   ##
=======================================
  Coverage   95.53%   95.53%           
=======================================
  Files          16       16           
  Lines        1075     1075           
=======================================
  Hits         1027     1027           
  Misses         48       48           

Files	Coverage Δ
api/String.h	90.00% <ø> (ø)

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[aentinger]

Hi @alranel ☕ 👋

Two minor points:

• Indendation does not match the rest of the file (probably a TAB vs SPACE issue?)
• Please provide a unit test that hard-codes the API expectation for this function.

[alranel]

Hi @aentinger!
Whoops, sorry for the bad indentation. I'm a spaces guy. Fixed, and unit test provided :)

[aentinger]

I'm a spaces guy.

I'm a spaces guy myself but since there are tabs in that file ... 🤷 got-to-go with the flow I suppose 😁

[aentinger]

Thank you for applying my suggestions! 🙇