Add generate messenger code artisan command

[metanite]

This will add an artisan command to generate messenger code in Facebook.

[codecov]

Codecov Report

Merging #94 into master will decrease coverage by 1.2%.
The diff coverage is 0%.

@@             Coverage Diff              @@
##             master      #94      +/-   ##
============================================
- Coverage      71.4%   70.19%   -1.21%     
- Complexity      479      483       +4     
============================================
  Files            50       51       +1     
  Lines          1336     1359      +23     
============================================
  Hits            954      954              
- Misses          382      405      +23

Impacted Files	Coverage Δ	Complexity Δ
src/Commands/GenerateMessengerCode.php	0% <0%> (ø)	4 <4> (?)

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