finished last bit of the gron outputter implementation

[traviscampbell]

also updated the test to show it's handling the pesky <, >, & chars.

[danielgtaylor]

Awesome, thank you!

[codecov]

Codecov Report

Merging #206 (a5dcceb) into main (3a541b4) will increase coverage by 0.04%.
The diff coverage is 100.00%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #206      +/-   ##
==========================================
+ Coverage   75.37%   75.41%   +0.04%     
==========================================
  Files          26       26              
  Lines        3513     3519       +6     
==========================================
+ Hits         2648     2654       +6     
  Misses        666      666              
  Partials      199      199              

Files Changed	Coverage Δ
cli/content.go	74.28% <100.00%> (+0.56%)	⬆️
cli/gron.go	100.00% <100.00%> (ø)

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