Allow install on PHP 8

[snapshotpl]

No description provided.

[codecov]

Codecov Report

Merging #54 (73a3ef0) into master (e9bef80) will increase coverage by 0.02%.
The diff coverage is 100.00%.

@@             Coverage Diff              @@
##             master      #54      +/-   ##
============================================
+ Coverage     92.13%   92.16%   +0.02%     
- Complexity      427      428       +1     
============================================
  Files            31       31              
  Lines           890      893       +3     
============================================
+ Hits            820      823       +3     
  Misses           70       70              

Impacted Files	Coverage Δ	Complexity Δ
src/Collection/Stream/Collectors.php	96.15% <ø> (ø)	9.00 <0.00> (ø)
src/Collection/Stream/Cons.php	100.00% <ø> (ø)	8.00 <0.00> (ø)
src/Collection/Traversable.php	100.00% <ø> (ø)	32.00 <0.00> (ø)
src/Collection/Set.php	90.00% <100.00%> (+0.34%)	38.00 <0.00> (+1.00)

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[akondas]

Thanks @snapshotpl 🍻