[Feature] Allow specifying direct dependencies

[IonBazan]

This PR fixes #39 by adding --direct option which limits the output to only direct dependencies (listed in either require or require-dev).

Additionally, JsonFormatter displays this additional information under direct: false|true key.

@royduin let me know what you think about this implementation. You can test this feature using:

composer global require ion-bazan/composer-diff:dev-feature/direct-dependencies

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 100.00%. Comparing base (b337dc8) to head (421225c).
Report is 1 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff             @@
##                main       #40   +/-   ##
===========================================
  Coverage     100.00%   100.00%           
- Complexity       228       241   +13     
===========================================
  Files             21        21           
  Lines            666       704   +38     
===========================================
+ Hits             666       704   +38     

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[royduin]

I didn't expect that so fast 🚀 looking good!! 💯