Added listener FlushLogContextListener for the logger context flushing

[tarampampam]

Description

Added

• Listener FlushLogContextListener for the logger context flushing

Related PR: laravel/octane#337

Checklist

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I wrote unit tests for my code (if tests is required for my changes)
• I have made changes in CHANGELOG.md file

[codecov]

Codecov Report

Merging #51 (e0602ad) into master (cd41168) will increase coverage by 0.07%.
The diff coverage is 87.50%.

@@             Coverage Diff              @@
##             master      #51      +/-   ##
============================================
+ Coverage     82.02%   82.10%   +0.07%     
- Complexity      257      260       +3     
============================================
  Files            54       55       +1     
  Lines           601      609       +8     
============================================
+ Hits            493      500       +7     
- Misses          108      109       +1     

Impacted Files	Coverage Δ
src/Defaults.php	100.00% <ø> (ø)
src/Listeners/FlushLogContextListener.php	87.50% <87.50%> (ø)

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[tarampampam]

Reminder: Unit tests are needed