add indent cli option

[losisin]

• Add -indent cli option that must be a positive even number - default is 4
• Add new line EOF to be POSIX compliant

Closes #61

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 98.85%. Comparing base (b453151) to head (613cb3a).
Report is 1 commits behind head on main.

❗ Current head 613cb3a differs from pull request most recent head 2a02a16. Consider uploading reports for the commit 2a02a16 to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #62      +/-   ##
==========================================
+ Coverage   98.83%   98.85%   +0.02%     
==========================================
  Files           6        6              
  Lines         342      349       +7     
==========================================
+ Hits          338      345       +7     
  Misses          2        2              
  Partials        2        2              

Flag	Coverage Δ
unittests	98.85% <100.00%> (+0.02%)	⬆️

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