Adding Queueable attribute

[msmakouz]

Q	A
Bugfix?	❌
Breaks BC?	❌
New feature?	✔️
Issues	#542

Interface already added:
https://github.com/spiral/framework/blob/master/src/Queue/src/QueueableInterface.php

[codecov]

Codecov Report

Merging #662 (56683e3) into master (3c9217f) will increase coverage by 0.02%.
The diff coverage is 100.00%.

@@             Coverage Diff              @@
##             master     #662      +/-   ##
============================================
+ Coverage     79.88%   79.90%   +0.02%     
- Complexity     6713     6721       +8     
============================================
  Files           755      757       +2     
  Lines         17005    17022      +17     
============================================
+ Hits          13585    13602      +17     
  Misses         3420     3420              

Impacted Files	Coverage Δ
src/Queue/src/Attribute/Queueable.php	100.00% <100.00%> (ø)
src/Queue/src/QueueableDetector.php	100.00% <100.00%> (ø)

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